DTV transmitting system and receiving system and method of processing broadcast signal

ABSTRACT

A television transmitting system includes an encoder, a data randomizing and expanding unit, a group formatter, a deinterleaver, and a packet formatter. The encoder codes enhanced data for error correction, permutes the coded data, and further codes the permuted data for error detection. The randomizing and expanding unit randomizes the error-detection-coded data and expands the randomized data. The group formatter forms a group of enhanced data having one or more data regions and inserts the expanded enhanced data into at least one of the regions. The deinterleaver deinterleaves the group of enhanced data, and the packet formatter generates enhanced data packets.

This application claims the benefit of the Korean Patent Application No.10-2006-0039117, filed on Apr. 29, 2006, which is hereby incorporated byreference as if fully set forth herein. Also, this application claimsthe benefit of the Korean Patent Application No. 10-2006-0089736, filedon Sep. 15, 2006, which is hereby incorporated by reference as if fullyset forth herein. This application also claims the benefit of U.S.Provisional Application No. 60/821,249, filed on Aug. 2, 2006, which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to television systems and methods ofprocessing a broadcast signal.

2. Discussion of the Related Art

Presently, the technology for processing digital signals is beingdeveloped at a vast rate, and, as a larger number of the population usesthe Internet, digital electric appliances, computers, and the Internetare being integrated. Therefore, in order to meet with the variousrequirements of the users, a system that can transmit diversesupplemental information in addition to video/audio data through adigital television channel needs to be developed.

Some users may assume that supplemental data broadcasting would beapplied by using a PC card or a portable device having a simple in-doorantenna attached thereto. However, when used indoors, the intensity ofthe signals may decrease due to a blockage caused by the walls ordisturbance caused by approaching or proximate mobile objects.Accordingly, the quality of the received digital signals may bedeteriorated due to a ghost effect and noise caused by reflected waves.However, unlike the general video/audio data, when transmitting thesupplemental data, the data that is to be transmitted should have a lowerror ratio. More specifically, in case of the video/audio data, errorsthat are not perceived or acknowledged through the eyes or ears of theuser can be ignored, since they do not cause any or much trouble.Conversely, in case of the supplemental data (e.g., program executionfile, stock information, etc.), an error even in a single bit may causea serious problem. Therefore, a system highly resistant to ghost effectsand noise is required to be developed.

The supplemental data are generally transmitted by a time-divisionmethod through the same channel as the video/audio data. However, withthe advent of digital broadcasting, digital television receiving systemsthat receive only video/audio data are already supplied to the market.Therefore, the supplemental data that are transmitted through the samechannel as the video/audio data should not influence the conventionalreceiving systems that are provided in the market. In other words, thismay be defined as the compatibility of broadcast system, and thesupplemental data broadcast system should be compatible with thebroadcast system. Herein, the supplemental data may also be referred toas enhanced data. Furthermore, in a poor channel environment, thereceiving performance of the conventional receiving system may bedeteriorated. More specifically, resistance to changes in channels andnoise is more highly required when using portable and/or mobilereceiving systems.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a DTV transmittingsystem and a DTV receiving system and a method of processing a broadcastsignal that substantially obviate one or more problems due tolimitations and disadvantages of the related art.

The present invention is to provide a DTV transmitting system and a DTVreceiving system and a method of processing a broadcast signal that issuitable for transmitting supplemental data and that is highly resistantto noise.

The present invention is to provide a DTV transmitting system and a DTVreceiving system and a method of processing a broadcast signal, whichare capable of performing additional encoding for enhanced data andtransmitting it, thereby enhancing receiving performance of a receivingsystem.

The present invention is to provide a DTV transmitting system and a DTVreceiving system and a method of processing a broadcast signal, whichcapable of multiplexing known data that are already known by a receivingsystem and/or a transmitting system and enhanced data, and main data,and transmitting it, thereby enhancing the receiving performance of thereceiving system.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, adigital television (DTV) transmitting system includes an encoder, a datarandomizing and expanding unit, a group formatter, a deinterleaver, anda packet formatter. The encoder codes enhanced data for errorcorrection, permutes the enhanced data coded for error correction, andcodes the permuted enhanced data for error detection. The datarandomizing and expanding unit randomizes the enhanced data coded forerror detection and expands the randomized data at an expansion rate of1/H. The group formatter forms a group of enhanced data having one ormore data regions and inserts the expanded enhanced data into at leastone of the data regions. The packet formatter generates enhanced datapackets including the deinterleaved enhanced data.

In another aspect of the present invention, a DTV receiving systemincludes a tuner, a demodulator, an equalizer, a block processor, a datadeformatter, and a frame decoder. The tuner tunes to a channel toreceive a digital broadcast signal including main and enhanced data. Thedemodulator demodulates the received broadcast signal, and the equalizercompensates channel distortion of the demodulated signal. The blockdecoder decodes each block of enhanced data in the channel-equalizedsignal. The data deformatter deformats the decoded enhanced data,removes null data included in the deformatted enhanced data, andderandomizes the null-data-removed enhanced data. The frame decoderdecodes the derandomized enhanced data for error detection, permutes theenhanced data decoded for error detection, and decodes the permutedenhanced data for error correction.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block diagram showing a structure of a digitalbroadcast transmitting system according to an embodiment of the presentinvention;

FIG. 2( a) to FIG. 2( d) illustrate process steps of error correctionencoding according to an embodiment of the present invention;

FIG. 3( a) and FIG. 3( b) illustrate process steps of row permutationaccording to an embodiment of the present invention;

FIG. 4( a) to FIG. 4( c) illustrate process steps of error detectionencoding according to an embodiment of the present invention;

FIG. 5 and FIG. 6 illustrate an examples of data configuration at beforeand after ends of a data deinterleaver in a digital broadcast receivingsystem according to the present invention;

FIG. 7( a) to FIG. 7( c) illustrate process steps of packet multiplexingin a digital broadcast transmitting system according to the presentinvention;

FIG. 8 illustrates a demodulating unit included a digital broadcastreceiving system according to an embodiment of the present invention;

FIG. 9 illustrates a block diagram of a digital broadcast (or televisionor DTV) transmitting system according to another embodiment of thepresent invention;

FIG. 10 and FIG. 11 illustrate another examples of data configuration atbefore and after ends of a data deinterleaver in a transmitting systemaccording to the present invention;

FIG. 12 illustrates a block diagram showing a general structure of ademodulating unit within a digital broadcast (or television or DTV)receiving system according to another embodiment of the presentinvention;

FIG. 13 illustrates a block diagram showing the structure of a digitalbroadcast (or television or DTV) receiving system according to anembodiment of the present invention; and

FIG. 14 illustrates a block diagram showing the structure of a digitalbroadcast (or television or DTV) receiving system according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. In addition,although the terms used in the present invention are selected fromgenerally known and used terms, some of the terms mentioned in thedescription of the present invention have been selected by the applicantat his or her discretion, the detailed meanings of which are describedin relevant parts of the description herein. Furthermore, it is requiredthat the present invention is understood, not simply by the actual termsused but by the meaning of each term lying within.

In the present invention, the enhanced data may either consist of dataincluding information such as program execution files, stockinformation, and so on, or consist of video/audio data. Additionally,the known data refer to data already known based upon a pre-determinedagreement between the transmitting system and the receiving system.Furthermore, the main data consist of data that can be received from theconventional receiving system, wherein the main data include video/audiodata. The present invention relates to performing additional encoding onthe enhanced data so as to provide robustness to the encoded data,thereby enabling the data to take strong countermeasures against theconstantly changing channel environment. As an embodiment of the presentinvention, at least any one of the error correction encoding and theerror detection encoding is performed on the enhanced data. Furthermore,a process of mixing (or permuting) several sets of the encoded data to apredetermined size may also be included.

FIG. 1 illustrates a block diagram showing a structure of a digitalbroadcast transmitting system according to an embodiment of the presentinvention. Referring to FIG. 1, the digital broadcast transmittingsystem includes a pre-processor 110, a packet multiplexer 121, a datarandomizer 122, a post-processor 130, an RS encoder/non-systematic RSencoder 141, a data interleaver 142, a parity replacer 143, anon-systematic RS encoder 144, a trellis encoding module 145, a framemultiplexer 146, and a transmitting unit 150. The pre-processor 110includes a RS frame encoder 111, a randomizer/byte expander 112, a groupformatter 113, a data deinterleaver 114, and a packet formatter 115. Thepost-processor 130 includes a RS parity place holder inserter 131, adata interleaver 132, a block processor 133, a data deinterleaver 134,and a RS parity place holder remover 135. Finally, the transmitting unit150 includes a pilot inserter 151, a modulator 152, and a RFup-converter 153.

In the present invention having the above-described structure, the maindata is inputted to the packet multiplexer 121, and the enhanced data isinputted to the pre-processor 110 which performs additional encoding, sothat the enhanced data can take strong countermeasures against noise andthe constantly changing channel environment. The RS frame encoder 111 ofthe pre-processor 110 receives the enhanced data and configures theframe in order to perform the additional encoding. Thereafter, thepre-processor 110 performs the additional encoding on the enhanced dataand, then, outputs the additionally encoded enhanced data to therandomizer/byte expander 112.

The operation of the RS frame encoder 111 will now be described indetail. According to an embodiment of the present invention, the RSframe encoder 111 performs at least any one of an error correctionencoding process and an error detection encoding process on the inputtedenhanced data so as to provide the data with robustness. In addition,the RS frame encoder 111 may also perform a process of permuting varioussets of enhanced data having a predetermined size by dispersing bursterrors that may occur due to a change in the frequency environment,thereby enabling the enhanced data to take countermeasures against aseverely poor and constantly and abruptly changing frequencyenvironment.

According to another environment of the present invention, the RS frameencoder 111 performs error correction encoding on the inputted enhanceddata, so as to add data required for error correction. Then, the RSframe encoder 111 performs a row permutation process for permuting datarow by row. Subsequently, the RS frame encoder 111 performs the errordetection encoding, thereby adding data required for error detection. Atthis point, as an example of the present invention, RS-coding is appliedfor the error correction encoding process, and a cyclic redundancy check(CRC) encoding is applied for the error detection process. Whenperforming the RS-coding, parity data that are used for the errorcorrection are generated. And, when performing the CRC encoding, CRCdata that are used for the error detection are generated.

FIG. 2 illustrates process steps of error correction encoding accordingto an embodiment of the present invention. Herein, the inputted enhanceddata are identified by units of a predetermined length (A). A pluralityof units of the identified predetermined length (A) is grouped to form aframe. Thereafter, RS-coding is performed on the newly formed framealong the direction of the row or column. In the present invention, thepredetermined length (A) will be referred to as a row for simplicity ofthe description. Herein, the value A is decided by the system designer.

For example, if the inputted enhanced data correspond to an MPEGtransport stream (TS) packet configured in 188-byte units, the firstMPEG synchronization byte is removed as shown in FIG. 2( a). Thereafter,a row (A) is formed on the 187 bytes as shown in FIG. 2( b). Herein, theMPEG synchronization byte is removed so that all enhanced data packetsare given the same value. If the inputted enhanced data do not include aremovable byte, or if the inputted enhanced data packet is not 187-bytelong, the inputted data are divided into units of 187 bytes, so thateach 187-byte data unit configures a row (A). When a row (A) is decidedaccording to the above-described process, a plurality of rows (A) isgrouped to form a RS frame. In the present invention, a method ofgrouping 67 rows (A) to form a RS frame, as shown in FIG. 2( c), will begiven as an example.

Subsequently, a (N,K)-RS-coding is performed on each column of the RSframe, so as to generate N-K number of parity bytes. Thereafter, thenewly created parity bytes are added to the end portion of thecorresponding column (i.e., the row following the 67^(th) row of thecorresponding column). According to the embodiment of the presentinvention, N is equal to ‘85’, and K is equal to ‘67’. Accordingly, thesize of the parity data that are added to each column, as shown in FIG.2( d), is equal to 18 bytes. When performing the (85,67)-RS-codingprocess on all 187 columns within the RS frame, a RS frame including onerow configured of 187 bytes and a column configured of 85 bytes may beobtained. More specifically, the RS encoded RS frame includes 85 rowseach configured of 187 bytes. As described above, the number of bytes,the number of rows configuring the RS frame, and the N and K values usedin the RS-coding process may vary depending upon the design of thesystem or any other circumstances and are not limited to theabove-described example.

FIG. 3 illustrates process steps of row permutation according to anembodiment of the present invention. Herein, FIG. 3 shows an example ofa row permutation process performed on the RS encoded data. Morespecifically, a plurality (or G number) of RS frames that are RS encodedare grouped to form a group. Thereafter, the row permutation process isperformed in group units. If it is assumed that one row is equal to 187bytes, and (85,67)-RS-coding is performed in FIG. 2, G number of RSframes configured of 85 rows, as shown in FIG. 3( a), is grouped to forma RS frame group consisting of 85*G number of 187-byte rows. When therow permutation is performed on the above-configured RS frame group byusing a predetermined method, the position of each row prior to the rowpermutation is different from the position of each row after performingthe row permutation. In other words, after performing the rowpermutation process, the i^(th) row of the RS frame group prior to therow permutation process, shown in FIG. 3( a), is placed to the j^(th)row of the RS frame group after the row permutation process, as shown inFIG. 3( b). The relation between i and j is shown in Equation 1 below.j=G(i mod S)+└i/S┘i=S(j mod G)+└j/G┘where 0≦i,j<SG   [Equation 1]

Each row of the RS frame group consists of 187 bytes even after the rowpermutation process is performed. At this point, the sizes of the RSframe prior to and after the row permutation process do not necessarilyhave to be identical to one another. However, the total number of rowswithin the RS frame groups both prior to and after the row permutationshould be identical to one another. For example, if the number of RSframes configuring the RS frame group prior to the row permutationprocess is G, and if it is assumed that the number of rows within one RSframe is 84, then there is no problem in the row permutation operationeven if the number of RS frames configuring the RS frame group after therow permutation process is 2G, and if the number of rows within one RSframe is 42. In other words, the sizes of each RS frame both prior toand after the row permutation process may be decided arbitrarily by thesystem designer.

FIG. 4( a) to FIG. 4( c) illustrate process steps of the CRC encodingprocess according to an embodiment of the present invention. Herein,FIG. 4( a) to FIG. 4( c) correspond to examples of performing the CRCencoding process on the data in which the row permutation process isperformed. The CRC data generated by the CRC encoding process are usedfor indicating whether damage has occurred due to an error in theenhanced data while being transmitted through a channel. The presentinvention may also use other error detection encoding methods other thanthe CRC encoding method. Alternatively, by using the error correctionencoding method, the overall error correction ability of the receivingsystem may be enhanced.

Referring to FIG. 4( a) to FIG. 4( c), the example off the process stepsof the error detection encoding method according to the presentinvention will now be described in detail. FIG. 4( a) illustrates anexample of an 8-bit CRC checksum being used as the CRC data. Morespecifically, a 1-byte (i.e., 8-bit) CRC checksum is generated for the187 bytes of each row. Then, the CRC checksum is added to thecorresponding row. Equation 2 below shows the example of a polynominalequation for generating the 1-byte CRC checksum for the 187 bytes.g(x)=x ⁶ +x ² +x ¹+1]  [Equation 2]

At this point, the 1-byte CRC checksum may be added to any position (orplace) within the corresponding row. Furthermore, as an embodiment ofthe present invention, FIG. 4( a) illustrates an example of the 1-byteCRC checksum being added to the end of the row, thereby configuring a188-byte row. FIG. 4( b) and FIG. 4( c) illustrate examples of a 16-bitCRC checksum being used as the CRC data. More specifically, a 2-byte(i.e., 16-bit) CRC checksum is generated for each two rows. Then, theCRC checksum is added to the corresponding row(s). Equation 3 belowshows the example of a polynominal equation for generating the 2-byteCRC checksum for each two rows (i.e., 374 bytes).g(x)=x ¹⁶ +x ¹² +x ⁵+1]  [Equation 3]

At this point, the 2-byte CRC checksum may be added to any position (orplace) within the corresponding two rows. The 2-byte CRC checksum may beadded to a predetermined position within the two corresponding rows,thereby dividing 376 bytes into two separate rows. More specifically,FIG. 4( b) illustrates an example of a 1-byte CRC checksum being addedto the end of each row, thereby configuring two 188-byte rows. And, FIG.4( c) illustrates an example of a 2-byte CRC checksum being added to theend of the second row, thereby configuring two 188-byte rows.

As described above, the CRC encoded data are outputted to therandomizer/byte expander 112. Herein, the randomizer/byte expander 112receives and randomizes the enhanced data in which robustness has beenenhanced due to the encoding and row permutation. Thereafter, byteexpansion is performed on the randomized data through the null datainsertion process and the repetition process. At this point, byrandomizing the enhanced data in the randomizer/byte expander 112, theprocess of randomizing the enhanced data at the randomizer 122 in alater process may be omitted. The randomizer identical to that of theconventional ATSC or other types of randomizer may be used forrandomizing the enhanced data. More specifically, a pseudo random bytegenerated from within the inputted 187-byte enhanced data may be used torandomize the enhanced data.

Additionally, the order of the randomizing process and the byteexpansion process may be altered. In other words, the randomizingprocess may first be performed as described above, which is thenfollowed by the byte expansion process. Alternatively, the byteexpansion process may first be performed, which is then followed by therandomizing process. The order of the processes may be selected inaccordance with the overall structure of the system.

The byte expansion process may vary depending upon the coding rate ofthe block processor 133 of the post-processor 130. More specifically, ifthe coding rate corresponds to a G/H coding rate, then G bytes areexpanded to H bytes. For example, if the coding rate corresponds to ½coding rate, then 1 byte is expanded to 2 bytes. And, if the coding rateis ¼, then 1 byte is expanded to 4 bytes. Therefore, if the coding rateis ½, then the RS encoded 85 188-byte units are expanded to 150 188-byteunits.

The enhanced data outputted from the randomizer/byte expander 112 isinputted to the group formatter 113. The group formatter 113 creates adata group in accordance with a pre-defined rule. Thereafter, the groupformatter 113 inserts the inputted enhanced data to the correspondingareas within the created data group. At this point, the data group maybe described as at least one layered area. Herein, the type of enhanceddata allocated to each area may vary depending upon the characteristicsof each layered area.

FIG. 5 illustrates an alignment of different data sets prior to the datadeinterleaving, and FIG. 6 illustrates an alignment of different datasets after the data deinterleaving. In other words, FIG. 5 correspondsto the data structure after being data interleaved, and FIG. 6corresponds to the data structure before being data interleaved. FIG. 5illustrates an example of a data group within a data structure prior tothe data deinterleaving, the data group being divided into three layeredareas: a head area, a body area, and a tail area. Accordingly, in thedata group that is data interleaved and outputted, the head area isfirst outputted, then the body area is outputted, and the tail area isoutputted last.

FIG. 5 and FIG. 6 each shows an example of 260 packets configuring thedata group. Herein, since the data interleaver operates periodically inunits of 52 packets, a 52*5n number of packets (wherein, n is aninteger) configure the data group. In addition, referring to the datagroup being inputted to the data deinterleaver, as shown in FIG. 5, thebody area is configured of a rectangular shape. Accordingly, FIG. 5illustrates an example of the head, body, and tail areas of the datagroup being configured so that the body area is entirely formed of theenhanced data and is not mixed with the main data. At this point, thebody area of the data group being inputted to the data deinterleaver maybe allocated so that the body area includes either at least a portion orthe entire portion of an area within the data group having the enhanceddata continuously outputted therefrom. Herein, the body area may alsoinclude an area having the enhanced data outputted non-continuously.

The data group is divided into three areas so that each area may be useddifferently. More specifically, referring to FIGS. 5 and 6, the areacorresponding to the body is configured only of enhanced data and is notinterfered by any main data, thereby showing a highly resistantreceiving quality. On the other hand, in each of the areas correspondingto the head and the tail, the enhanced data set is alternately mixedwith the main data sets due to the output order of the interleaver.Thus, the receiving quality of the head and tail areas is relativelypoorer than that of the body area.

Furthermore, when using a system inserting and transmitting the knowndata to the data group, and when a long and continuous set of known datais to be inserted periodically in the enhanced data, the known data maybe inserted in an area in which the enhanced data are not mixed with themain data based upon the output order from the data interleaver. Morespecifically, in the body area of FIGS. 5 and 6, a predetermined lengthof known data may be periodically inserted in the body area. However, itis difficult to periodically insert the known data in the head area andthe tail area, and it is also difficult to insert a long and continuousset of known data. Therefore, the group formatter 113 inserts theenhanced data inserted in the corresponding area within theabove-described data group.

For example, the group formatter 113 allocates the received enhanceddata to the body area. And, apart from the enhanced data, the groupformatter 113 also separately allocates signaling information indicatingthe overall transmission information to the body area. In other words,the signaling information corresponds to information required by thereceiving system for receiving and processing the data included datagroup. Herein, the signaling information includes data groupinformation, multiplexing information, and so on. Furthermore, as shownin FIG. 5, the group formatter 113 also inserts an MPEG header placeholder, a non-systematic RS parity place holder, and a main data placeholder in relation with the data deinterleaving. Referring to FIG. 5,the main data place is allocated because the enhanced data and the maindata are alternately mixed in the head and tail areas based upon theinput of the data deinterleaver. In the output data that have been datainterleaved, the place holder for the MPEG header is allocated to thevery beginning of each packet.

The group formatter 113 either inserts the known data generated by apre-decided method in a corresponding area, or inserts a known dataplace holder in a corresponding area so as to insert the known data in alater process. Moreover, a place holder for initializing the trellisencoding module 145 is inserted in the corresponding area. For example,the initialization data place holder may be inserted in front of theknown data sequence. The data group having either the data or the placeholder inserted therein by the group formatter 113 is inputted to thedata deinterleaver 114. Referring to FIG. 5, whenever required in alater process, the head and tail areas may be used for the enhanced dataor other information data or data used for supporting the enhanced data.

The data deinterleaver 114 performs an inverse process of the datainterleaver on the inputted data group and, then, outputs thedeinterleaved data group to the packet formatter 115. More specifically,when the data group having the format shown in FIG. 5 is inputted to thedata deinterleaver 114, the data group is deinterleaved, as shown inFIG. 6, and outputted to the packet formatter 115. Herein, only theportions corresponding to the data group are shown in FIG. 6. Among thedeinterleaved and inputted data, the packet formatter 115 removes themain data place holder and the RS parity place holder that have beenallocated for the deinterleaving process and inserts the known data inplace of the removed place holders. Alternatively, the known data placeholder may be directly outputted without any modification for thereplacement insertion in the post-processor 130.

Thereafter, the packet formatter 115 configures the data within the datagroup packet that is formatted as described above, as a 188-byte unitMPEG TS packet. Then, the packet formatter 115 provides the configured188-byte unit MPEG TS packet to the packet multiplexer 121. The packetmultiplexer 121 multiplexes the 188-byte enhanced data packet and themain data packet outputted from the packet formatter 115 according to apre-defined multiplexing method. Then, the multiplexed packets areoutputted to the data randomizer 122. The packet multiplexer 121 will bedescribed in more detail in a later process. When the inputted datacorrespond to the main data packet, the data randomizer 122 performs arandomizing process identical to that of the conventional randomizer.More specifically, the MPEG synchronization byte within the main datapacket is discarded (or deleted). Then, the remaining 187 bytes arerandomized by using a pseudo random byte generated from within the datarandomizer 122. Subsequently, the randomized data bytes are outputted tothe post-processor 130.

However, when the inputted data correspond to the enhanced data packet,the MPEG synchronization byte among the four bytes included in theenhanced data packet is discarded (or deleted) and only the remaining 3bytes are randomized. The remaining portion of the enhanced dataexcluding the MPEG header is not randomized and outputted directly tothe post-processor 130. This is because a randomizing process hasalready been performed on the enhanced data in the randomizer/byteexpander 112. The known data (or known data place holder) and theinitialization data place holder included in the enhanced data packetmay either be randomized or not be randomized, and only the informationon the place holders is transmitted to the receiving system.

The data randomized or bypassed from the data randomizer 122 areinputted to the RS parity place holder inserter 131 of thepost-processor 130. If the inputted data correspond to the 187-byte maindata packet, the RS parity place holder inserter 131 inserts a 20-byteRS parity place holder at the end of the 187-byte data. Then, the RSparity place holder inserter 131 outputs the processed data to the datainterleaver 132. Alternatively, if the inputted data correspond to the187-byte enhanced data packet, a 20-byte RS parity place holder isinserted within the packet for a non-systematic RS-coding process thatis to be performed in a later process. Thereafter, the bytes within theenhanced data packet are inserted in the remaining 187 byte places,which are then outputted to the data interleaver 132. The datainterleaver 132 data interleaves the output of the RS parity placeholder inserter 131 and outputs the interleaved data to the blockprocessor 133.

The block processor 133 performed additional encoding only on theenhanced data outputted from the data interleaver 132. For example, if a2-byte expansion has been performed in the randomizer/byte expander 112,the block processor 133 encodes the enhanced data at a ½ coding rate.Alternatively, if a 4-byte expansion has been performed in therandomizer/byte expander 112, the block processor 133 encodes theenhanced data at a ¼ coding rate. In addition, the main data or the RSparity place holder are/is bypassed without any modification.Furthermore, the known data (or known data place holder) and theinitialization data place holder may be bypassed without modification orreplaced with the known data generated from the block processor 133 andthen outputted.

The data encoded, replaced, and bypassed by the block processor 133 areinputted to the data deinterleaver 134. Then, the data deinterleaver 134performs an inverse process of the data interleaver 132, therebydeinterleaving the inputted data and outputted the deinterleaved data tothe RS parity place holder remover 135. Herein, the RS parity placeholder remover 135 removes the 20-byte RS parity place holder added bythe RS parity place holder inserter 131 so that the data interleaver 132and the data deinterleaver 134 may be operated. Thereafter, the parityplace holder removed data are outputted to the RS encoder/non-systematicRS encoder 141. At this point, if the inputted data correspond to themain data packet, the last 20-byte RS parity place holders among the 207bytes are removed. And, if the inputted data correspond to the enhanceddata packet, the 20-byte RS parity place holders that are inserted inthe 207 bytes in order to perform the non-systematic RS-coding processare removed. Herein, when the main data sequentially pass through the RSparity place holder inserter 131, the data interleaver 132, the blockprocessor 133, the data deinterleaver 134, and the RS parity placeholder remover 135, the processed main data become identical to the maindata being inputted to the RS parity place holder inserter 131.

The RS encoder/non-systematic RS encoder 141 RS encodes the inputteddata so as to add an 20-byte RS parity, thereby outputting the processedand parity-added data to the data interleaver 142. At this point, if theinputted data correspond to the main data packet, the RSencoder/non-systematic RS encoder 141 performs a systematic RS-codingprocess identical to that of the conventional broadcast system on theinputted data, thereby adding the 20-byte RS parity at the end of the187-byte data. Alternatively, if the inputted data correspond to theenhanced data packet, each place of the 20 parity bytes is decidedwithin the packet. Thereafter, the 20 bytes of RS parity gained byperforming the non-systematic RS-coding are respectively inserted in thedecided parity byte places.

The data interleaver 142 corresponds to a byte unit convolutionalinterleaver. The same interleaving rule as that of the above-described(first) data interleaver 132 is applied to the (second) data interleaver142 mentioned herein. The (second) data interleaver 142 performs exactlythe same operation as that of the (first) data interleaver 132. Howeverthe two data interleavers 132 and 142 are differentiated from oneanother for simplicity of the description with respect to the positionof each data interleaver. Similarly, the (second) data deinterleaver 134performs exactly the same operation as that of the (first) datadeinterleaver 114. The two data deinterleavers 114 and 134 are alsodifferentiated from one another for simplicity of the description withrespect to the position of each data deinterleaver. Herein, the datadeinterleaver performed the inverse process of the data interleaver.Therefore, when a particular input sequence is inputted to the datainterleaver so as to obtain (or output) an output sequence, and when theobtained output sequence is inputted to the data deinterleaver, theoutput obtained from the data deinterleaver becomes identical to theparticular input sequence initially inputted to the data interleaver.The output of the data interleaver 142 is inputted to the parityreplacer 143 and the non-systematic RS encoder 144.

Meanwhile, a memory within the trellis encoding module 145 should firstbe initialized in order to allow the output data of the trellis encodingmodule 145, which is positioned after the parity replacer 143, to becomethe known data defined based upon an agreement between the receivingsystem and the transmitting system. More specifically, the memory of thetrellis encoding module 145 should first be initialized before the knowndata sequence being inputted is encoded. At this point, the beginning ofthe known data sequence that is inputted corresponds to theinitialization data place holder included by the group formatter 113 andnot the actual known data. Therefore, a process of generatinginitialization data right before the trellis-encoding of the known datasequence being inputted and a process of replacing the initializationdata place holder of the corresponding trellis encoder memory with thenewly generated initialization data are required. This is to ensure thebackward-compatibility with the conventional receiving system.

Additionally, the value of the trellis memory initialization data isdecided in accordance with a previous state of the memory in the trellisencoding module 145, and the initialization data are generatedaccordingly. Furthermore, due to the replaced initialization data, aprocess of recalculating the RS parity and a process of replacing thenewly calculated RS parity with the RS parity outputted from the datainterleaver 142 are required. Therefore, the non-systematic RS encoder144 receives the enhanced data packet including the initialization dataplace holder that is to be replaced with the initialization data fromthe data interleaver, and the non-systematic RS encoder 144 receives theinitialization data from the trellis encoding module 145. Then, thenon-systematic RS encoder 144 calculates a new non-systematic RS parityand outputs the newly calculated non-systematic RS parity to the parityreplacer 143. Thereafter, the parity replacer 143 selects the output ofthe data interleaver 142 as the data within the enhanced data packet,and the parity replacer 143 selects the output of the non-systematic RSencoder 144 as the RS parity.

Meanwhile, when the main data packet is inputted or when the enhanceddata packet, which does not include the initialization data place holderthat is to be replaced, is inputted, the parity replacer 143 selects thedata outputted from the data interleaver 142 and the RS parity andoutputs the selects output data and RS parity to the trellis encodingmodule 145 without any modification. The trellis encoding module 145modifies the byte-unit data to symbol-unit data. Then, the trellisencoding module 145 12-way interleaves and trellis-encodes the modifieddata, so as to output the processed data to the frame multiplexer 146.The frame multiplexer 146 inserts field and segment synchronizationsignals in the output of the trellis encoding module 145 and outputs theprocessed data to the transmitting unit 150. Herein, the transmittingunit 150 includes a pilot inserter 151, a modulator 152, and a radiofrequency (RF) up-converter 153. The transmitting unit 150 operatesidentically as in the conventional transmitting system. Therefore, adetailed description of the same will be omitted for simplicity.

Packet Multiplexer

The packet multiplexer 121 multiplexes a 188-byte enhanced data packetand the main data packet outputted from the packet formatter 115 andoutputs the multiplexed data packets. The multiplexing method may beadjusted by various factors related to the design of the systemaccording to the present invention. FIG. 7( a) to FIG. 7( c) illustratean example of the process of multiplexing the enhanced data packet andthe main data packet. Herein, the enhanced data are transmitted in burstunits.

Referring to the time axis of FIG. 7( a), an enhanced data burst sectionoccupying an N field and a main data section occupying an M field arerepeated. In the N field, the enhanced data packet and the main datapacket within the data group are multiplexed and outputted. And, in theM field, only the main data packet is outputted. FIG. 7( b) and FIG. 7(c) are enlargements of the enhanced data burst section having the lengthof N field along the time axis. More specifically, FIG. 7( b) is anenlargement of the enhanced data burst section along the time axis basedupon the input of the (first) data interleaver 132 or the (second) datainterleaver 142. And, FIG. 7( c) is an enlargement of the enhanced databurst section along the time axis based upon the output of the datainterleaver. Referring to FIG. 7( c), the data group and the main dataof one field is repeatedly transmitted. Herein, the enhanced data of thehead and tail areas within the data group are alternately mixed with themain data in accordance with the output order of the interleaver.Therefore, the main data may be included in the field section whereinthe data group is transmitted.

As shown in FIGS. 6( a) to 6(c), when a field occupied by the data groupis positioned (or placed) at each of the very first and the very lastfields within the enhanced data burst section, and when a field occupiedby the main data is positioned between the two fields occupied by thedata group, the total number (N) of fields included in the enhanced databurst section becomes an odd number. At this point, the enhanced databurst section and the main data section are not necessarily required tobe in data field units and may be set to be in segment units. Inaddition, the enhanced data burst section and the main data section arenot required to be periodically repeated. And, the amount of main datapositioned between two neighboring data group within the enhanced databurst second may be modified in accordance with the design andregulations of the system. Further, when the enhanced data aretransmitted in the above-described burst structure, and in a receivingsystem receiving only the enhanced data, the power is turned on onlyduring the burst section so as to receive the data. On the other hand,during the main data section in which only the main data are received,the power is turned off so as to prevent the main data from beingreceived, thereby reducing the amount of the power consumed in thereceiving system.

As described above, the packet multiplexer 121 receives the main datapacket and the data group outputted from the packet formatter 115 andtransmits the received data to the burst structure shown in FIG. 7( a).At this point, as shown in FIG. 7( b), the data group and the main datapacket within one enhanced data burst section are multiplexed andoutputted. The output of the packet multiplexer 121 undergoes a seriesof process including the data interleaving process, and then, at thepoint the processed data are inputted to the frame multiplexer 146, theprocessed data are configured to have the enhanced data burst structure,as shown in FIG. 7( c). In this case, the structure of one data groupincludes a head area corresponding to the first 52 segments consistingof enhanced data alternately mixed with the main data, a body areacorresponding to 20B segments consisting only of the main data, and atail area corresponding to 52 segments consisting of enhanced dataalternately mixed with the main data.

FIG. 8 illustrates an example of a demodulating unit included a digitalbroadcast receiving system receiving data transmitted by theabove-described digital broadcast transmitting system, therebyrecovering the received data to its initial state by demodulating andequalizing the received data. The demodulating unit according to thepresent invention, shown in FIG. 8, includes a demodulator 401,equalizer 402, a known sequence detector 403, a block decoder 404, adata deformatter 405, a RS frame decoder 406, a data deinterleaver 407,a RS decoder 408, and a main data derandomizer 409.

More specifically, the received signal through a tuner inputs to thedemodulator 401 and the known sequence detector 403. The demodulator 401performs automatic gain control, carrier recovery and timing recovery,etc., for the inputted signal to generate a baseband signal, and thenoutput it to the equalizer 402 and the known sequence detector 403.

The equalizer 402 compensates the distortion of the channel included inthe demodulated signal and then outputs the error-compensated signal tothe block decoder 404.

At this point, the known sequence detector 403 detects the known datasequence place inserted by the transmitting end from the input/outputdata of the demodulator 401 (i.e., the data prior to the demodulation orthe data after the modulation). Thereafter, the place information alongwith the symbol sequence of the known data sequence, which is generatedfrom the detected place, is outputted to the demodulator 401, theequalizer 402, and the block decoder 404. Further, the known sequencedetector 403 outputs information related to the enhanced dataadditionally encoded by the transmitting end and the main data that havenot been additionally encoded to the block decoder 404. Herein, theoutputted information is outputted to allow the enhanced data and themain data to be differentiated by the block decoder 404 of the receivingend and to find out the starting point of a block in the enhancedencoder. Although the connection state is not shown in FIG. 8, theinformation detected by the known sequence detector 403 may be usedthroughout almost the entire receiving system. Herein, the detectedinformation may also be used in the data deformatter 405 and in the RSframe decoder 406.

The demodulator 401 uses the known data symbol sequence during thetiming and/or carrier recovery, thereby enhancing the demodulatingquality. Similarly, the equalizer 402 uses the known data sequence,thereby enhancing the equalizing quality. Furthermore, the decodingresult of the block decoder 404 may also be fed-back to the equalizer402, thereby enhancing the equalizing quality.

Meanwhile, when the data being inputted to the block decoder 404correspond to the enhanced data being additionally coded andtrellis-encoded by the transmitting end, the equalizer 402 performs aninverse process of the transmitting end by additionally decoding andtrellis-decoding the inputted enhanced data. On the other hand, when thedata being inputted correspond to the main data being trellis-encodedonly and not additionally coded, the equalizer 402 only performstrellis-decoding on the inputted main data. The data group decoded bythe block decoder 404 is inputted to the data deformatter 405, and themain data packet is inputted to the data deinterleaver 407. Morespecifically, when the inputted data correspond to the main data, theblock decoder 404 performs Viterbi-decoding on the input data so as tooutput a hard decision value or to perform hard decision on a softdecision value and output the hard-decided result. Meanwhile, when theinputted data correspond to the enhanced data, the block decoder 404outputs a hard decision value or a soft decision value on the inputtedenhanced value.

When the inputted data correspond to the enhanced data, the blockdecoder 404 performs a decoding process on the data encoded by the blockprocessor 133 and trellis encoding module 145 of the DTV transmittingsystem. At this point, the data outputted from the RS frame encoder 111of the pre-processor 110 included in the DTV transmitting system maycorrespond to an external code, and the data outputted from each of theblock processor 133 and the trellis encoding module 145 may correspondto an internal code.

When decoding such concatenated codes, the decoder of the internal codeshould output a soft decision value, so that the external codingperformance can be enhanced. Therefore, the block decoder 404 may alsooutput a hard decision value on the enhanced data and, preferably, asoft decision value may be outputted when required. More specifically,any one of a soft decision value and a hard decision value is outputtedwith respect to the enhanced data depending upon the overall design orconditions of the system, and a hard decision value is outputted withrespect to the main data.

Meanwhile, the data deinterleaver 407, the RS decoder 408, and the maindata derandomizer 409 are blocks required for receiving the main data.Therefore, these blocks may not be required in the structure of a DTVreceiving system that only receives the enhanced data. The datadeinterleaver 407 performs an inverse process of the data interleaverincluded in the DTV transmitting system. More specifically, the datadeinterleaver 407 deinterleaves the main data and outputs thedeinterleaved data to the RS decoder 408. The RS decoder 408 performs RSdecoding on the deinterleaved data and outputs the RS-decoded data tothe main data derandomizer 409. The main data derandomizer 409 receivesthe output of the RS decoder 408 and generates a pseudo random data byteidentical to that of the randomizer included in the DTV transmittingsystem. Thereafter, the main data derandomizer 409 performs a bitwiseexclusive OR (XOR) operation on the generated pseudo random data byte,thereby inserting the MPEG synchronization bytes to the beginning ofeach packet so as to output the data in 188-byte main data packet units.

The data being outputted from the block decoder 404 are inputted to thedata deformatter 405 in the format of the data group, as shown in FIG.5. At this point, the data deformatter 405 already knows theconfiguration of the input data. Therefore, the signaling informationhaving the system information and enhanced data are differentiated inthe body area within the data group. In addition, the data deformatter405 removes the known data, trellis initialization data, and MPEG headerthat were inserted in the main data and data group and also removes theRS parity added by one of the RS encoder/non-systematic RS encoder 141and non systematic RS encoder 144 of the DTV transmitting system.

Furthermore, a derandomizing process is performed as an inverse processof the randomizer/byte expander in the DTV transmitting system on theenhanced data. At this point, the null data byte used for the byteexpansion by the byte expander may be or may not be required to beremoved. In other words, depending upon design of the DTV receivingsystem, the removal of the byte, which has been expanded by the byteexpander of the DTV transmitting system, may be required. However, ifthe null data byte inserted during the byte expansion is removed andoutputted by the block decoder 404, the expanded byte is not required tobe removed. However, if the removal of the expanded byte is required,the order of the byte removal process and the derandomizing process mayvary depending upon the structure of the DTV transmitting system. Morespecifically, if the byte expansion is performed after the randomizingprocess in the DTV transmitting system, then the byte removal process isfirst performed before performing the derandomizing process in the DTVreceiving system. Conversely, if the order of the process is changed inthe DTV transmitting system, the order of the respective processes inthe DTV receiving system is also changed.

When performing the derandomizing process, if the RS frame decoder 406requires a soft decision in a later process, and if, therefore, theblock decoder 404 receives a soft decision value it is difficult toperform an XOR operation between the soft decision and the pseudo randombit, which is used for the derandomizing process. Accordingly, when anXOR operation is performed between the pseudo random bit and the softdecision value of the enhanced data bit, and when the pseudo random bitis equal to ‘1’, the data deformatter 405 changes the code of the softdecision value and then outputs the changed code. On the other hand, ifthe pseudo random bit is equal to ‘0’, the data deformatter 405 outputsthe soft decision value without any change in the code. Thus, the stateof the soft decision may be maintained and transmitted to the RS framedecoder 406.

If the pseudo random bit is equal to ‘1’ as described above, the code ofthe soft decision value is changed because, when an XOR operation isperformed between the pseudo random bit and the input data in therandomizer of the transmitting system, and when the pseudo random bit isequal to ‘1’, the code of the output data bit becomes the opposite ofthe input data (i.e., 0 XOR 1=1 and 1 XOR 0=0). More specifically, ifthe pseudo random bit generated from the data deformatter 405 is equalto ‘1’, and when an XOR operation is performed on the hard decisionvalue of the enhanced data bit, the XOR-operated value becomes theopposite value of the hard decision value. Therefore, when the softdecision value is outputted, a code opposite to that of the softdecision value is outputted.

The RS frame decoder 406 performs an inverse process of the RS frameencoder 11 in the DTV transmitting system. For example, if the blockprocessor 133 of the transmitting system (or DTV transmitter) performsan encoding process at a ½ coding rate, then a RS frame having 85packets (or rows) configured of 188 bytes is inputted to the RS framedecoder 406. The RS frame decoder 406 gathers (or groups) G number ofsuch RS frames, thereby forming a RS frame group having 85*G number ofRS frames. Furthermore, when using a 1-byte (i.e., 0-bit) CRC checksum,as shown in FIG. 4( a), each 188-byte packet is checked for any existingerror. Thereafter, the 1-byte checksum is removed, thereby leaving 187bytes. Subsequently, the presence of an error is marked on an error flagcorresponding to the 187-byte packet. On the other hand, when using a2-byte (i.e., 16-bit) CRC checksum, as shown in FIG. 4( b) and FIG. 4(c), each two 188-byte packets are checked for any existing error.Thereafter, the 2-byte checksums is removed, thereby creating two187-byte packets. Subsequently, the presence of an error is marked on anerror flag corresponding to each 187-byte packet. At this point, whenusing the 2-byte checksum, both packets should be marked to have anerror or to have no error.

After performing an error check on each row using the checksum asdescribed above, an inverse process of the row permutation process(shown in FIG. 3) is performed on the RS frame group configured of 85*Gnumber of 187-byte packets. Thus, the 85*G number of 187-byte packetsare aligned in the initial order prior to undergoing the row permutationprocess in the transmitting system. Thereafter, the RS frame group isdivided into G number of RS frames configured of 85 187-byte packets.When performing the inverse process of the row permutation process, theerror flag indicating the presence of an error in each packet (or row)is also converted and succeeded.

Each of the RS frames is configured to have the same structure as a bytematrix of 187×85. Subsequently, by decoding each of the 187(85,67)-RS-coded columns within the RS frame, 67 187-byte rows may beobtained along with the error correction. Furthermore, the MPEGsynchronization data byte, which was removed by the transmitting system,is added to the foremost end of each 187-byte row, thereby outputtingthe enhanced TS packet recovered to 188 bytes. At this point, whenRS-decoding each of the RS frames, if the number of rows having errorbased upon the CRC error check result is equal to or smaller than themaximum number of errors that can be erasure-corrected when beingRS-decoded in the column direction, an erasure correction process may beperformed as the RS-decoding process, thereby maximizing the errorcorrection ability.

FIG. 9 illustrates a block diagram showing the structure of a digitalbroadcast transmitting system according to an embodiment of the presentinvention. The digital broadcast transmitting system includes apre-processor 510, a packet multiplexer 521, a data randomizer 522, aReed-Solomon (RS) encoder/non-systematic RS encoder 523, a datainterleaver 524, a parity byte replacer 525, a non-systematic RS encoder526, a frame multiplexer 528, and a transmitting unit 530. Thepre-processor 510 includes an enhanced data randomizer 511, a RS frameencoder 512, a block processor 513, a group formatter 514, a datadeinterleaver 515, and a packet formatter 516.

In the present invention having the above-described structure, main dataare inputted to the packet multiplexer 521. Enhanced data are inputtedto the enhanced data randomizer 511 of the pre-processor 510, wherein anadditional coding process is performed so that the present invention canrespond swiftly and appropriately against noise and change in channel.The enhanced data randomizer 511 randomizes the received enhanced dataand outputs the randomized enhanced data to the RS frame encoder 512. Atthis point, by having the enhanced data randomizer 511 perform therandomizing process on the enhanced data, the randomizing process on theenhanced data by the data randomizer 522 in a later process may beomitted. Either the randomizer of the conventional broadcast system maybe used as the randomizer for randomizing the enhanced data, or anyother type of randomizer may be used herein.

The RS frame encoder 512 receives the randomized enhanced data andperforms at least one of an error correction coding process and an errordetection coding process on the received data. Accordingly, by providingrobustness to the enhanced data, the data can scatter group error thatmay occur due to a change in the frequency environment. Thus, the datacan respond appropriately to the frequency environment which is verypoor and liable to change. The RS frame multiplexer 512 also includes aprocess of mixing in row units many sets of enhanced data each having apre-determined size. By performing an error correction coding process onthe inputted enhanced data, the RS frame encoder 512 adds data requiredfor the error correction and, then, performs an error detection codingprocess, thereby adding data required for the error detection process.The error correction coding uses the RS coding method, and the errordetection coding uses the cyclic redundancy check (CRC) coding method.When performing the RS coding process, parity data required for theerror correction are generated. And, when performing the CRC codingprocess, CRC data required for the error detection are generated.

The RS frame encoder 512 performs CRC coding on the RS coded enhanceddata in order to create the CRC code. The CRC code that is generated bythe CRC coding process may be used to indicate whether the enhanced datahave been damaged by an error while being transmitted through thechannel. The present invention may adopt other types of error detectioncoding methods, apart from the CRC coding method, and may also use theerror correction coding method so as to enhance the overall errorcorrection ability of the receiving system. For example, assuming thatthe size of one RS frame is 187*N bytes, that (235,187)-RS codingprocess is performed on each column within the RS frame, and that a CRCcoding process using a 2-byte (i.e., 16-bit) CRC checksum, then a RSframe having the size of 187*N bytes is expanded to a RS frame of235*(N+2) bytes. The RS frame expanded by the RS frame encoder 512 isinputted to the block processor 513. The block processor 513 codes theRS-coded and CRC-coded enhanced data at a coding rate of G/H. Then, theblock processor 513 outputs the G/H-rate coded enhanced data to thegroup formatter 514. In order to do so, the block processor 513identifies the block data bytes being inputted from the RS frame encoder512 as bits.

The block processor 513 may receive supplemental information data suchas signaling information, which include information on the system, andidentifies the supplemental information data bytes as data bits. Herein,the supplemental information data, such as the signaling information,may equally pass through the enhanced data randomizer 511 and the RSframe encoder 512 so as to be inputted to the block processor 513.Alternatively, the supplemental information data may be directlyinputted to the block processor 513 without passing through the enhanceddata randomizer 511 and the RS frame encoder 512. The signalinginformation corresponds to information required for receiving andprocessing data included in the data group in the receiving system. Suchsignaling information includes data group information, multiplexinginformation, and burst information.

As a G/H-rate encoder, the block processor 513 codes the inputted dataat a coding rate of G/H and then outputs the G/H-rate coded data. Forexample, if 1 bit of the input data is coded to 2 bits and outputted,then G is equal to 1 and H is equal to 2 (i.e., G=1 and H=2).Alternatively, if 1 bit of the input data is coded to 4 bits andoutputted, then G is equal to 1 and H is equal to 4 (i.e., G=1 and H=4).As an example of the present invention, it is assumed that the blockprocessor 513 performs a coding process at a coding rate of ½ (alsoreferred to as a ½-rate coding process) or a coding process at a codingrate of ¼ (also referred to as a ¼-rate coding process). Morespecifically, the block processor 513 codes the received enhanced dataand supplemental information data, such as the signaling information, ateither a coding rate of ½ or a coding rate of ¼. Thereafter, thesupplemental information data, such as the signaling information, areidentified and processed as enhanced data.

Since the ¼-rate coding process has a higher coding rate than the ½-ratecoding process, greater error correction ability may be provided.Therefore, in a later process, by allocating the ¼-rate coded data in anarea with deficient receiving performance within the group formatter514, and by allocating the ½-rate coded data in an area with excellentreceiving performance, the difference in the overall performance may bereduced. More specifically, in case of performing the ½-rate codingprocess, the block processor 513 receives 1 bit and codes the received 1bit to 2 bits (i.e., 1 symbol). Then, the block processor 513 outputsthe processed 2 bits (or 1 symbol). On the other hand, in case ofperforming the ¼-rate coding process, the block processor 513 receives 1bit and codes the received 1 bit to 4 bits (i.e., 2 symbols). Then, theblock processor 513 outputs the processed 4 bits (or 2 symbols).Additionally, the block processor 513 performs a block interleavingprocess in symbol units on the symbol-coded data. Subsequently, theblock processor 513 converts to bytes the data symbols that areblock-interleaved and have the order rearranged.

The group formatter 514 inserts the enhanced data outputted from theblock processor 513 (herein, the enhanced data may include supplementalinformation data such as signaling information including transmissioninformation) in a corresponding area within the data group, which isconfigured according to a pre-defined rule. Furthermore, in relationwith the data deinterleaving process, various types of places holders orknown data are also inserted in corresponding areas within the datagroup.

At this point, the data group may be described by at least onehierarchical area. Herein, the data allocated to the each area may varydepending upon the characteristic of each hierarchical area.Additionally, each data group may be configured to include a fieldsynchronization signal.

In another example given in the present invention, a data group isdivided into A, B, and C regions in a data configuration prior to datadeinterleaving.

FIG. 10 illustrates an alignment of data after being data interleavedand identified, and FIG. 11 illustrates an alignment of data beforebeing data interleaved and identified. More specifically, a datastructure identical to that shown in FIG. 10 is transmitted to areceiving system. Also, the data group configured to have the samestructure as the data structure shown in FIG. 10 is inputted to the datadeinterleaver 515.

As described above, FIG. 10 illustrates a data structure prior to datadeinterleaving that is divided into 3 regions, such as region A, regionB, and region C. Also, in the present invention, each of the regions Ato C is further divided into a plurality of regions. Referring to FIG.10, region A is divided into 5 regions (A1 to A5), region B is dividedinto 2 regions (B1 and B2), and region C is divided into 3 regions (C1to C3). Herein, regions A to C are identified as regions having similarreceiving performances within the data group. Herein, the type ofenhanced data, which are inputted, may also vary depending upon thecharacteristic of each region.

In the example of the present invention, the data structure is dividedinto regions A to C based upon the level of interference of the maindata. Herein, the data group is divided into a plurality of regions tobe used for different purposes. More specifically, a region of the maindata having no interference or a very low interference level may beconsidered to have a more resistant (or stronger) receiving performanceas compared to regions having higher interference levels. Additionally,when using a system inserting and transmitting known data in the datagroup, and when consecutively long known data are to be periodicallyinserted in the enhanced data, the known data having a predeterminedlength may be periodically inserted in the region having no interferencefrom the main data (e.g., region A). However, due to interference fromthe main data, it is difficult to periodically insert known data andalso to insert consecutively long known data to a region havinginterference from the main data (e.g., region B and region C)

Hereinafter, examples of allocating data to region A (A1 to A5), regionB (B1 and B2), and region C (C1 to C3) will now be described in detailwith reference to FIG. 10. The data group size, the number ofhierarchically divided regions within the data group and the size ofeach region, and the number of enhanced data bytes that can be insertedin each hierarchically divided region of FIG. 10 are merely examplesgiven to facilitate the understanding of the present invention. Herein,the group formatter 514 creates a data group including places in whichfield synchronization bytes are to be inserted, so as to create the datagroup that will hereinafter be described in detail.

More specifically, region A is a region within the data group in which along known data sequence may be periodically inserted, and in whichincludes regions wherein the main data are not mixed (e.g., A1 to A5).Also, region A includes a region (e.g., A1) located between a fieldsynchronization region and the region in which the first known datasequence is to be inserted. The field synchronization region has thelength of one segment (i.e., 832 symbols) existing in an ATSC system.

For example, referring to FIG. 10, 2428 bytes of the enhanced data maybe inserted in region A1, 2580 bytes may be inserted in region A2, 2772bytes may be inserted in region A3, 2472 bytes may be inserted in regionA4, and 2772 bytes may be inserted in region A5. Herein, trellisinitialization data or known data, MPEG header, and RS parity are notincluded in the enhanced data. As described above, when region Aincludes a known data sequence at both ends, the receiving system useschannel information that can obtain known data or field synchronizationdata, so as to perform equalization, thereby providing enforcedequalization performance.

Also, region B includes a region located within 8 segments at thebeginning of a field synchronization region within the data group(chronologically placed before region A1) (e.g., region B1), and aregion located within 8 segments behind the very last known datasequence which is inserted in the data group (e.g., region B2). Forexample, 930 bytes of the enhanced data may be inserted in the regionB1, and 1350 bytes may be inserted in region B2. Similarly, trellisinitialization data or known data, MPEG header, and RS parity are notincluded in the enhanced data. In case of region B, the receiving systemmay perform equalization by using channel information obtained from thefield synchronization section. Alternatively, the receiving system mayalso perform equalization by using channel information that may beobtained from the last known data sequence, thereby enabling the systemto respond to the channel changes.

Region C includes a region located within 30 segments including andpreceding the 9^(th) segment of the field synchronization region(chronologically located before region A) (e.g., region C1), a regionlocated within 12 segments including and following the 9^(th) segment ofthe very last known data sequence within the data group (chronologicallylocated after region A) (e.g., region C2), and a region located in 32segments after the region C2 (e.g., region C3). For example, 1272 bytesof the enhanced data may be inserted in the region C1, 1560 bytes may beinserted in region C2, and 1312 bytes may be inserted in region C3.Similarly, trellis initialization data or known data, MPEG header, andRS parity are not included in the enhanced data. Herein, region C (e.g.,region C1) is located chronologically earlier than (or before) region A.

Since region C (e.g., region C1) is located further apart from the fieldsynchronization region which corresponds to the closest known dataregion, the receiving system may use the channel information obtainedfrom the field synchronization data when performing channelequalization. Alternatively, the receiving system may also use the mostrecent channel information of a previous data group. Furthermore, inregion C (e.g., region C2 and region C3) located before region A, thereceiving system may use the channel information obtained from the lastknown data sequence to perform equalization. However, when the channelsare subject to fast and frequent changes, the equalization may not beperformed perfectly. Therefore, the equalization performance of region Cmay be deteriorated as compared to that of region B.

When it is assumed that the data group is allocated with a plurality ofhierarchically divided regions, as described above, the block processor513 may encode the enhanced data, which are to be inserted to eachregion based upon the characteristic of each hierarchical region, at adifferent coding rate. For example, the block processor 513 may encodethe enhanced data, which are to be inserted in regions A1 to A5 ofregion A, at a coding rate of ½. Then, the group formatter 514 mayinsert the ½-rate encoded enhanced data to regions A1 to A5.

The block processor 513 may encode the enhanced data, which are to beinserted in regions B1 and B2 of region B, at a coding rate of ¼ havinghigher error correction ability as compared to the ½-coding rate. Then,the group formatter 514 inserts the ¼-rate coded enhanced data in regionB1 and region B2. Furthermore, the block processor 513 may encode theenhanced data, which are to be inserted in regions C1 to C3 of region C,at a coding rate of ¼ or a coding rate having higher error correctionability than the ¼-coding rate. Then, the group formatter 514 may eitherinsert the encoded enhanced data to regions C1 to C3, as describedabove, or leave the data in a reserved region for future usage.

In addition, the group formatter 514 also inserts supplemental data,such as signaling information that notifies the overall transmissioninformation, other than the enhanced data in the data group. Also, apartfrom the encoded enhanced data outputted from the block processor 513,the group formatter 514 also inserts MPEG header place holders,non-systematic RS parity place holders, main data place holders, whichare related to data deinterleaving in a later process, as shown in FIG.10. Herein, the main data place holders are inserted because theenhanced data bytes and the main data bytes are alternately mixed withone another in regions B and C based upon the input of the datadeinterleaver, as shown in FIG. 10. For example, based upon the dataoutputted after data deinterleaving, the place holder for the MPEGheader may be allocated at the very beginning of each packet.

Furthermore, the group formatter 514 either inserts known data generatedin accordance with a pre-determined method or inserts known data placeholders for inserting the known data in a later process. Additionally,place holders for initializing the trellis encoder 527 are also insertedin the corresponding regions. For example, the initialization data placeholders may be inserted in the beginning of the known data sequence.Herein, the size of the enhanced data that can be inserted in a datagroup may vary in accordance with the sizes of the trellisinitialization place holders or known data (or known data placeholders), MPEG header place holders, and RS parity place holders.

The output of the group formatter 514 is inputted to the datadeinterleaver 515. And, the data deinterleaver 515 deinterleaves data byperforming an inverse process of the data interleaver on the data andplace holders within the data group, which are then outputted to thepacket formatter 516. More specifically, when the data and place holderswithin the data group configured, as shown in FIG. 10, are deinterleavedby the data deinterleaver 515, the data group being outputted to thepacket formatter 516 is configured to have the structure shown in FIG.11.

Among the data deinterleaved and inputted, the packet formatter 516removes the main data place holder and RS parity place holder that wereallocated for the deinterleaving process from the inputted deinterleaveddata. Thereafter, the remaining portion of the corresponding data isgrouped, and 4 bytes of MPEG header are inserted therein. The 4-byteMPEG header is configured of a 1-byte MPEG synchronization byte added tothe 3-byte MPEG header place holder.

When the group formatter 514 inserts the known data place holder, thepacket formatter 516 may either insert actual known data in the knowndata place holder or output the known data place holder without anychange or modification for a replacement insertion in a later process.Afterwards, the packet formatter 516 divides the data within theabove-described packet-formatted data group into 188-byte unit enhanceddata packets (i.e., MPEG TS packets), which are then provided to thepacket multiplexer 521. The packet multiplexer 521 multiplexes the188-byte unit enhanced data packet and main data packet outputted fromthe packet formatter 516 according to a pre-defined multiplexing method.Subsequently, the multiplexed data packets are outputted to the datarandomizer 522. The multiplexing method may be modified or altered inaccordance with diverse variables of the system design.

As an example of the multiplexing method of the packet multiplexer 521,the enhanced data burst section and the main data section may beidentified along a time axis (or a chronological axis) and may bealternately repeated. At this point, the enhanced data burst section maytransmit at least one data group, and the main data section may transmitonly the main data. The enhanced data burst section may also transmitthe main data. If the enhanced data are outputted in a burst structure,as described above, the receiving system receiving only the enhanceddata may turn the power on only during the burst section so as toreceive the enhanced data, and may turn the power off during the maindata section in which main data are transmitted, so as to prevent themain data from being received, thereby reducing the power consumption ofthe receiving system.

When the data being inputted correspond to the main data packet, thedata randomizer 522 performs the same randomizing process of theconventional randomizer. More specifically, the MPEG synchronizationbyte included in the main data packet is discarded and a pseudo randombyte generated from the remaining 187 bytes is used so as to randomizethe data. Thereafter, the randomized data are outputted to the RSencoder/non-systematic RS encoder 523. However, when the inputted datacorrespond to the enhanced data packet, the MPEG synchronization byte ofthe 4-byte MPEG header included in the enhanced data packet isdiscarded, and data randomizing is performed only on the remaining3-byte MPEG header. Randomizing is not performed on the remainingportion of the enhanced data. Instead, the remaining portion of theenhanced data is outputted to the RS encoder/non-systematic RS encoder523. This is because the randomizing process has already been performedon the enhanced data by the enhanced data randomizer 511 in an earlierprocess. Herein, a data randomizing process may or may not be performedon the known data (or known data place holder) and the initializationdata place holder included in the enhanced data packet.

The RS encoder/non-systematic RS encoder 523 RS-codes the datarandomized by the data randomizer 522 or the data bypassing the datarandomizer 522. Then, the RS encoder/non-systematic RS encoder 523 addsa 20-byte RS parity to the coded data, thereby outputting theRS-parity-added data to the data interleaver 524. At this point, if theinputted data correspond to the main data packet, the RSencoder/non-systematic RS encoder 523 performs a systematic RS-codingprocess identical to that of the conventional receiving system on theinputted data, thereby adding the 20-byte RS parity at the end of the187-byte data. Alternatively, if the inputted data correspond to theenhanced data packet, the 20 bytes of RS parity gained by performing thenon-systematic RS-coding are respectively inserted in the decided paritybyte places within the enhanced data packet. Herein, the datainterleaver 524 corresponds to a byte unit convolutional interleaver.The output of the data interleaver 524 is inputted to the parity bytereplacer 525 and the non-systematic RS encoder 526.

Meanwhile, a memory within the trellis encoding module 527, which ispositioned after the parity byte replacer 525, should first beinitialized in order to allow the output data of the trellis encodingmodule 527 so as to become the known data defined based upon anagreement between the receiving system and the transmitting system. Morespecifically, the memory of the trellis encoding module 527 should firstbe initialized before the known data sequence being inputted istrellis-encoded. At this point, the beginning of the known data sequencethat is inputted corresponds to the initialization data place holderinserted by the group formatter 514 and not the actual known data.Therefore, a process of generating initialization data right before thetrellis-encoding of the known data sequence being inputted and a processof replacing the initialization data place holder of the correspondingtrellis encoding module memory with the newly generated initializationdata are required.

A value of the trellis memory initialization data is decided based uponthe memory status of the trellis encoding module 527, thereby generatingthe trellis memory initialization data accordingly. Due to the influenceof the replace initialization data, a process of recalculating the RSparity, thereby replacing the RS parity outputted from the trellisencoding module 527 with the newly calculated RS parity is required.Accordingly, the non-systematic RS encoder 526 receives the enhanceddata packet including the initialization data place holder that is to bereplaced with the initialization data from the data interleaver 524 andalso receives the initialization data from the trellis encoding module527. Thereafter, among the received enhanced data packet, theinitialization data place holder is replaced with the initializationdata. Subsequently, the RS parity data added to the enhanced data packetare removed. Then, a new non-systematic RS parity is calculated andoutputted to the parity byte replacer 525. Accordingly, the parity bytereplacer 525 selects the output of the data interleaver 524 as the datawithin the enhanced data packet, and selects the output of thenon-systematic RS encoder 526 as the RS parity. Thereafter, the paritybyte replacer 525 outputs the selected data.

Meanwhile, if the main data packet is inputted, or if the enhanced datapacket that does not include the initialization data place holder thatis to be replaced, the parity byte replacer 525 selects the data and RSparity outputted from the data interleaver 524 and directly outputs theselected data to the trellis encoding module 527 without modification.The trellis encoding module 527 converts the byte-unit data tosymbol-unit data and 12-way interleaves and trellis-encodes theconverted data, which are then outputted to the frame multiplexer 528.The frame multiplexer 528 inserts field synchronization and segmentsynchronization signals in the output of the trellis encoding module 527and then outputs the processed data to the transmitting unit 530.Herein, the transmitting unit 530 includes a pilot inserter 531, amodulator 532, and a radio frequency (RF) up-converter 533. Theoperation of the transmitting unit 530 is identical to the conventionaltransmitters. Therefore, a detailed description of the same will beomitted for simplicity.

FIG. 12 illustrates a block diagram of a demodulating unit included inthe receiving system according to another embodiment of the presentinvention. Herein, the demodulating unit may effectively process signalstransmitted from the transmitting system shown in FIG. 9. Referring toFIG. 12, the demodulating unit includes a demodulator 601, a channelequalizer 602, a known sequence detector 603, a block decoder 604, anenhanced data deformatter 605, a RS frame decoder 606, an enhanced dataderandomizer 607, a data deinterleaver 608, a RS decoder 609, and a maindata derandomizer 910. For simplicity, the demodulator 601, the channelequalizer 602, the known sequence detector 603, the block decoder 604,the enhanced data deformatter 605, the RS frame decoder 606, and theenhanced data derandomizer 607 will be referred to as an enhanced dataprocessor. And, the data deinterleaver 608, the RS decoder 609, and themain data derandomizer 910 will be referred to as a main data processor.

More specifically, the enhanced data including known data and the maindata are received through the tuner and inputted to the demodulator 601and the known sequence detector 603. The demodulator 601 performsautomatic gain control, carrier wave recovery, and timing recovery onthe data that are being inputted, thereby creating baseband data, whichare then outputted to the equalizer 602 and the known sequence detector603. The equalizer 602 compensates the distortion within the channelincluded in the demodulated data. Then, the equalizer 602 outputs thecompensated data to the block decoder 604.

At this point, the known sequence detector 603 detects the known dataplace inserted by the transmitting system to the input/output data ofthe demodulator 601 (i.e., data prior to demodulation or data afterdemodulation). Then, along with the position information, the knownsequence detector 603 outputs the symbol sequence of the known datagenerated from the corresponding position to the demodulator 601 and theequalizer 602. Additionally, the known sequence detector 603 outputsinformation enabling the block decoder 604 to identify the enhanced databeing additionally encoded by the transmitting system and the main datathat are not additionally encoded to the block decoder 604. Furthermore,although the connection is not shown in FIG. 12, the informationdetected by the known sequence detector 603 may be used in the overallreceiving system and may also be used in the enhanced data formatter 605and the RS frame decoder 606.

By using the known data symbol sequence when performing the timingrecovery or carrier wave recovery, the demodulating performance of thedemodulator 601 may be enhanced. Similarly, by using the known data, thechannel equalizing performance of the channel equalizer 602 may beenhanced. Furthermore, by feeding-back the decoding result of the blockdecoder 604 to the channel equalizer 602, the channel equalizingperformance may also be enhanced.

The equalizer 602 may perform channel equalization by using a pluralityof methods. An example of estimating a channel impulse response (CIR) soas to perform channel equalization will be given in the description ofthe present invention. Most particularly, an example of estimating theCIR in accordance with each region within the data group, which ishierarchically divided and transmitted from the transmitting system, andapplying each CIR differently will also be described herein.Furthermore, by using the known data, the place and contents of which isknown in accordance with an agreement between the transmitting systemand the receiving system, and the field synchronization data, so as toestimate the CIR, the present invention may be able to perform channelequalization with more stability.

Herein, the data group that is inputted for the equalization process isdivided into regions A to C, as shown in FIG. 10. More specifically, inthe example of the present invention, each region A, B, and C arefurther divided into regions A1 to A5, regions B1 and B2, and regions C1to C3, respectively. Referring to FIG. 10, the CIR that is estimatedfrom the field synchronization data in the data structure is referred toas CIR_FS. Alternatively, the CIRs that are estimated from each of the 5known data sequences existing in region A are sequentially referred toas CIR_N0, CIR_N1, CIR_N2, CIR_N3, and CIR_N4.

As described above, the present invention uses the CIR estimated fromthe field synchronization data and the known data sequences in order toperform channel equalization on data within the data group. At thispoint, each of the estimated CIRs may be directly used in accordancewith the characteristics of each region within the data group.Alternatively, a plurality of the estimated CIRs may also be eitherinterpolated or extrapolated so as to create a new CIR, which is thenused for the channel equalization process.

Herein, when a value F(Q) of a function F(x) at a particular point Q anda value F(S) of the function F(x) at another particular point S areknown, interpolation refers to estimating a function value of a pointwithin the section between points Q and S. Linear interpolationcorresponds to the simplest form among a wide range of interpolationoperations. The linear interpolation described herein is merelyexemplary among a wide range of possible interpolation methods. And,therefore, the present invention is not limited only to the examples setforth herein.

Alternatively, when a value F(Q) of a function F(x) at a particularpoint Q and a value F(S) of the function F(x) at another particularpoint S are known, extrapolation refers to estimating a function valueof a point outside of the section between points Q and S. Linearextrapolation is the simplest form among a wide range of extrapolationoperations. Similarly, the linear extrapolation described herein ismerely exemplary among a wide range of possible extrapolation methods.And, therefore, the present invention is not limited only to theexamples set forth herein.

More specifically, in case of region C1, any one of the CIR_N4 estimatedfrom a previous data group, the CIR_FS estimated from the current datagroup that is to be processed with channel equalization, and a new CIRgenerated by extrapolating the CIR_FS of the current data group and theCIR_N0 may be used to perform channel equalization. Alternatively, incase of region B1, a variety of methods may be applied as described inthe case for region C1. For example, a new CIR created by linearlyextrapolating the CIR_FS estimated from the current data group and theCIR_N0 may be used to perform channel equalization. Also, the CIR_FSestimated from the current data group may also be used to performchannel equalization. Finally, in case of region A1, a new CIR may becreated by interpolating the CIR_FS estimated from the current datagroup and CIR_N0, which is then used to perform channel equalization.Furthermore, any one of the CIR_FS estimated from the current data groupand CIR_N0 may be used to perform channel equalization.

In case of regions A2 to A5, CIR_N(i−1) estimated from the current datagroup and CIR_N(i) may be interpolated to create a new CIR and use thenewly created CIR to perform channel equalization. Also, any one of theCIR_N(i−1) estimated from the current data group and the CIR_N(i) may beused to perform channel equalization. Alternatively, in case of regionsB2, C2, and C3, CIR_N3 and CIR_N4 both estimated from the current datagroup may be extrapolated to create a new CIR, which is then used toperform the channel equalization process. Furthermore, the CIR_N4estimated from the current data group may be used to perform the channelequalization process. Accordingly, an optimum performance may beobtained when performing channel equalization on the data inserted inthe data group. The methods of obtaining the CIRs required forperforming the channel equalization process in each region within thedata group, as described above, are merely examples given to facilitatethe understanding of the present invention, A wider range of methods mayalso be used herein. And, therefore, the present invention will not onlybe limited to the examples given in the description set forth herein.

Meanwhile, if the data being channel equalized and then inputted to theblock decoder 604 correspond to the enhanced data on which additionalencoding and trellis encoding are both performed by the transmittingsystem, trellis-decoding and additional decoding processes are performedas inverse processes of the transmitting system. Alternatively, if thedata being channel equalized and then inputted to the block decoder 604correspond to the main data on which additional encoding is notperformed and only trellis-encoding is performed by the transmittingsystem, only the trellis-decoding process is performed. The data groupdecoded by the block decoder 604 is inputted to the enhanced datadeformatter 605, and the main data packet is inputted to the datadeinterleaver 608.

More specifically, if the inputted data correspond to the main data, theblock decoder 604 performs Viterbi decoding on the inputted data, so asto either output a hard decision value or hard-decide a soft decisionvalue and output the hard-decided result. On the other hand, if theinputted correspond to the enhanced data, the block decoder 604 outputseither a hard decision value or a soft decision value on the inputtedenhanced data. In other words, if the data inputted to the block decoder604 correspond to the enhanced data, the block decoder 604 performs adecoding process on the data encoded by the block processor and thetrellis encoder of the transmitting system. At this point, the output ofthe RS frame encoder included in the pre-processor of the transmittingsystem becomes an external code, and the output of the block processorand the trellis encoder becomes an internal code. In order to showmaximum performance of the external code when decoding such connectioncodes, the decoder of the internal code should output a soft decisionvalue. Therefore, the block decoder 604 may output a hard decision valueon the enhanced data. However, when required, it is more preferable thatthe block decoder 604 outputs a soft decision value.

The present invention may also be used for configuring a reliability mapusing the soft decision value. The reliability map determines andindicates whether a byte corresponding to a group of 8 bits decided bythe code of the soft decision value is reliable. For example, when anabsolute value of the soft decision value exceeds a pre-determinedthreshold value, the value of the bit corresponding to the soft decisionvalue code is determined to be reliable. However, if the absolute valuedoes not exceed the pre-determined threshold value, then the value ofthe corresponding bit is determined to be not reliable. Further, if atleast one bit among the group of 8 bits, which are determined based uponthe soft decision value, is determined to be not reliable, then thereliability map indicates that the entire byte is not reliable. Herein,the process of determining the reliability by 1-bit units is merelyexemplary. The corresponding byte may also be indicated to be notreliable if a plurality of bits (e.g., 4 bits) is determined to be notreliable.

Conversely, when all of the bits are determined to be reliable withinone byte (i.e., when the absolute value of the soft value of all bitsexceeds the pre-determined threshold value), then the reliability mapdetermines and indicates that the corresponding data byte is reliable.Similarly, when more than 4 bits are determined to be reliable withinone data byte, then the reliability map determines and indicates thatthe corresponding data byte is reliable. The estimated numbers aremerely exemplary and do not limit the scope and spirit of the presentinvention. Herein, the reliability map may be used when performing errorcorrection decoding processes.

Meanwhile, the data deinterleaver 608, the RS decoder 609, and the maindata derandomizer 910 are blocks required for receiving the main data.These blocks may not be required in a receiving system structure thatreceives only the enhanced data. The data deinterleaver 608 performs aninverse process of the data interleaver of the transmitting system. Morespecifically, the data deinterleaver 608 deinterleaves the main databeing outputted from the block decode 604 and outputs the deinterleaveddata to the RS decoder 609. The RS decoder 609 performs systematic RSdecoding on the deinterleaved data and outputs the systematicallydecoded data to the main data derandomizer 910. The main dataderandomizer 910 receives the data outputted from the RS decoder 609 soas to generate the same pseudo random byte as that of the randomizer inthe transmitting system. The main data derandomizer 910 then performs abitwise exclusive OR (XOR) operation on the generated pseudo random databyte, thereby inserting the MPEG synchronization bytes to the beginningof each packet so as to output the data in 188-byte main data packetunits.

Herein, the format of the data being outputted to the enhanced datadeformatter 605 from the block decoder 604 is a data group format. Atthis point, the enhanced data deformatter 605 already knows thestructure of the input data. Therefore, the enhanced data deformatter605 identifies the system information including signaling informationand the enhanced data from the data group. Thereafter, the identifiedsignaling information is transmitted to where the system information isrequired, and the enhanced data are outputted to the RS frame decoder606. The enhanced data deformatter 605 removes the known data, trellisinitialization data, and MPEG header that were included in the main dataand the data group and also removes the RS parity that was added by theRS encoder/non-systematic RS encoder of the transmitting system.Thereafter, the processed data are outputted to the RS frame decoder606.

More specifically, the RS frame decoder 606 receives the RS-coded andCRC-coded enhanced data from the enhanced data deformatter 605 so as toconfigure the RS frame. The RS frame decoder 606 performs an inverseprocess of the RS frame encoder included in the transmitting system,thereby correcting the errors within the RS frame. Then, the 1-byte MPEGsynchronization byte, which was removed during the RS frame codingprocess, is added to the error corrected enhanced data packet.Subsequently, the processed data are outputted to the enhanced dataderandomizer 607. Herein, the enhanced data derandomizer 607 performs aderandomizing process, which corresponds to an inverse process of theenhanced data randomizer included in the transmitting system, on thereceived enhanced data. Then, by outputting the processed data, theenhanced data transmitted from the transmitting system can be obtained.

According to an embodiment of the present invention, the RS framedecoder 606 may also be configured as follows. The RS frame decoder 606may perform a CRC syndrome check on the RS frame, thereby verifyingwhether or not an error has occurred in each row. Subsequently, the CRCchecksum is removed and the presence of an error is indicated on a CRCerror flag corresponding to each row. Then, a RS decoding process isperformed on the RS frame having the CRC checksum removed in a columndirection. At this point, depending upon the number of CRC error flags,a RS erasure decoding process may be performed. More specifically, bychecking the CRC error flags corresponding to each row within the RSframe, the number of CRC error flags may be determined whether it isgreater or smaller than the maximum number of errors, when RS decodingthe number of rows with errors (or erroneous rows) in the columndirection. Herein, the maximum number of errors corresponds to thenumber of parity bytes inserted during the RS decoding process. As anexample of the present invention, it is assumed that 48 parity bytes areadded to each column.

If the number of rows with CRC errors is equal to or smaller than themaximum number of errors (e.g., 43), which may be corrected by the RSerasure decoding process, the RS erasure decoding process is performedon the RS frame in the column direction. Thereafter, the 48 bytes ofparity data that were added at the end of each column are removed.However, if the number of rows with CRC errors is greater than themaximum number of errors (e.g., 48), which may be corrected by the RSerasure decoding process, the RS erasure decoding process cannot beperformed. In this case, the error may be corrected by performing ageneral RS decoding process.

As another embodiment of the present invention, the error correctionability may be enhanced by using the reliability map created whenconfiguring the RS frame from the soft decision value. Morespecifically, the RS frame decoder 606 compares the absolute value ofthe soft decision value obtained from the block decoder 604 to thepre-determined threshold value so as to determine the reliability of thebit values that are decided by the code of the corresponding softdecision value. Then, 8 bits are grouped to configure a byte. Then, thereliability information of the corresponding byte is indicated on thereliability map. Therefore, even if a specific row is determined to haveCRC errors as a result of the CRC syndrome checking process of thecorresponding row, it is not assumed that all of the data bytes includedin the corresponding row have error. Instead, only the data bytes thatare determined to be not reliable, after referring to the reliabilityinformation on the reliability map, are set to have errors. In otherwords, regardless of the presence of CRC errors in the correspondingrow, only the data bytes that are determined to be not reliable (orunreliable) by the reliability map are set as erasure points.

Thereafter, if the number of erasure points for each column is equal toor smaller than the maximum number of errors (e.g., 48), the RS erasuredecoding process is performed on the corresponding the column.Conversely, if the number of erasure points is greater than the maximumnumber of errors (e.g., 48), which may be corrected by the RS erasuredecoding process, a general decoding process is performed on thecorresponding column. In other words, if the number of rows having CRCerrors is greater than the maximum number of errors (e.g., 48), whichmay be corrected by the RS erasure decoding process, either a RS erasuredecoding process or a general RS decoding process is performed on aparticular column in accordance with the number of erasure point withinthe corresponding column, wherein the number is decided based upon thereliability information on the reliability map. When the above-describedprocess is performed, the error correction decoding process is performedin the direction of all of the columns included in the RS frame.Thereafter, the 48 bytes of parity data added to the end of each columnare removed.

FIG. 13 illustrates a block diagram showing the structure of a digitalbroadcast receiving system according to an embodiment of the presentinvention. Referring to FIG. 13, the digital broadcast receiving systemincludes a tuner 701, a demodulating unit 702, a demultiplexer 703, anaudio decoder 704, a video decoder 705, a native TV application manager706, a channel manager 707, a channel map 708, a first memory 709, adata decoder 710, a second memory 711, a system manager 712, a databroadcasting application manager 713, a storage controller 714, and athird memory 715. Herein, the third memory 715 is a mass storage device,such as a hard disk drive (HDD) or a memory chip. The tuner 701 tunes afrequency of a specific channel through any one of an antenna, cable,and satellite. Then, the tuner 701 down-converts the tuned frequency toan intermediate frequency (IF), which is then outputted to thedemodulating unit 702. At this point, the tuner 701 is controlled by thechannel manager 707. Additionally, the result and strength of thebroadcast signal of the tuned channel are also reported to the channelmanager 707. The data that are being received by the frequency of thetuned specific channel include main data, enhanced data, and table datafor decoding the main data and enhanced data.

In the embodiment of the present invention, examples of the enhanceddata may include data provided for data service, such as Javaapplication data, HTML application data, XML data, and so on. The dataprovided for such data services may correspond either to a Java classfile for the Java application, or to a directory file designatingpositions (or locations) of such files. Furthermore, such data may alsocorrespond to an audio file and/or a video file used in eachapplication. The data services may include weather forecast services,traffic information services, stock information services, servicesproviding information quiz programs providing audience participationservices, real time poll, user interactive education programs, gamingservices, services providing information on soap opera (or TV series)synopsis, characters, original sound track, filing sites, servicesproviding information on past sports matches, profiles andaccomplishments of sports players, product information and productordering services, services providing information on broadcast programsby media type, airing time, subject, and so on. The types of dataservices described above are only exemplary and are not limited only tothe examples given herein. Furthermore, depending upon the embodiment ofthe present invention, the enhanced data may correspond to meta data Forexample, the meta data use the XML application so as to be transmittedthrough a DSM-CC protocol.

The demodulating unit 702 performs demodulation and channel equalizationon the signal being outputted from the tuner 701, thereby identifyingthe main data and the enhanced data. Thereafter, the identified maindata and enhanced data are outputted in TS packet units. Examples of thedemodulating unit 702 are shown in FIG. 8 and FIG. 12. The demodulatingunit shown in FIG. 8 and FIG. 12 is merely exemplary and the scope ofthe present invention is not limited to the examples set forth herein.In the embodiment given as an example of the present invention, only theenhanced data packet outputted from the demodulating unit 702 isinputted to the demultiplexer 703. In this case, the main data packet isinputted to another demultiplexer (not shown) that processes main datapackets. Herein, the storage controller 714 is also connected to theother demultiplexer in order to store the main data after processing themain data packets. The demultiplexer of the present invention may alsobe designed to process both enhanced data packets and main data packetsin a single demultiplexer.

The storage controller 714 is interfaced with the demultipelxer so as tocontrol instant recording, reserved (or pre-programmed) recording, timeshift, and so on of the enhanced data and/or main data. For example,when one of instant recording, reserved (or pre-programmed) recording,and time shift is set and programmed in the receiving system (orreceiver) shown in FIG. 13, the corresponding enhanced data and/or maindata that are inputted to the demultiplexer are stored in the thirdmemory 715 in accordance with the control of the storage controller 714.The third memory 715 may be described as a temporary storage area and/ora permanent storage area. Herein, the temporary storage area is used forthe time shifting function, and the permanent storage area is used for apermanent storage of data according to the user's choice (or decision).

When the data stored in the third memory 715 need to be reproduced (orplayed), the storage controller 714 reads the corresponding data storedin the third memory 715 and outputs the read data to the correspondingdemultiplexer (e.g., the enhanced data are outputted to thedemultiplexer 703 shown in FIG. 13). At this point, according to theembodiment of the present invention, since the storage capacity of thethird memory 715 is limited, the compression encoded enhanced dataand/or main data that are being inputted are directly stored in thethird memory 715 without any modification for the efficiency of thestorage capacity. In this case, depending upon the reproduction (orreading) command, the data read from the third memory 715 pass troughthe demultiplexer so as to be inputted to the corresponding decoder,thereby being restored to the initial state.

The storage controller 714 may control the reproduction (or play),fast-forward, rewind, slow motion, instant replay functions of the datathat are already stored in the third memory 715 or presently beingbuffered. Herein, the instant replay function corresponds to repeatedlyviewing scenes that the viewer (or user) wishes to view once again. Theinstant replay function may be performed on stored data and also on datathat are currently being received in real time by associating theinstant replay function with the time shift function. If the data beinginputted correspond to the analog format, for example, if thetransmission mode is NTSC, PAL, and so on, the storage controller 714compression encodes the inputted data and stored the compression-encodeddata to the third memory 715. In order to do so, the storage controller714 may include an encoder, wherein the encoder may be embodied as oneof software, middleware, and hardware. Herein, an MPEG encoder may beused as the encoder according to an embodiment of the present invention.The encoder may also be provided outside of the storage controller 714.

Meanwhile, in order to prevent illegal duplication (or copies) of theinput data being stored in the third memory 715, the storage controller714 scrambles the input data and stores the scrambled data in the thirdmemory 715. Accordingly, the storage controller 714 may include ascramble algorithm for scrambling the data stored in the third memory715 and a descramble algorithm for descrambling the data read from thethird memory 715. Herein, the definition of scramble includesencryption, and the definition of descramble includes decryption. Thescramble method may include using an arbitrary key (e.g., control word)to modify a desired set of data, and also a method of mixing signals.

Meanwhile, the demultiplexer 703 receives the real-time data outputtedfrom the demodulating unit 702 or the data read from the third memory715 and demultiplexes the received data. In the example given in thepresent invention, the demultiplexer 703 performs demultiplexing on theenhanced data packet. Therefore, in the present invention, the receivingand processing of the enhanced data will be described in detail. Itshould also be noted that a detailed description of the processing ofthe main data will be omitted for simplicity starting from thedescription of the demultiplexer 703 and the subsequent elements.

The demultiplexer 703 demultiplexes enhanced data and program specificinformation/program and system information protocol (PSI/PSIP) tablesfrom the enhanced data packet inputted in accordance with the control ofthe data decoder 710. Thereafter, the demultiplexed enhanced data andPSI/PSIP tables are outputted to the data decoder 710 in a sectionformat. In order to extract the enhanced data from the channel throughwhich enhanced data are transmitted and to decode the extracted enhanceddata, system information is required. Such system information may alsobe referred to as service information. The system information mayinclude channel information, event information, etc. In the embodimentof the present invention, the PSI/PSIP tables are applied as the systeminformation. However, the present invention is not limited to theexample set forth herein. More specifically, regardless of the name, anyprotocol transmitting system information in a table format may beapplied in the present invention.

The PSI table is an MPEG-2 g system standard defined for identifying thechannels and the programs. The PSIP table is an advanced televisionsystems committee (ATSC) standard that can identify the channels and theprograms. The PSI table may include a program association table (PAT), aconditional access table (CAT), a program map table (PMT), and a networkinformation table (NIT). Herein, the PAT corresponds to specialinformation that is transmitted by a data packet having a PID of ‘0’.The PAT transmits PID information of the PMT and PID information of theNIT corresponding to each program. The CAT transmits information on apaid broadcast system used by the transmitting system. The PMT transmitsPID information of a transport stream (TS) packet, in which programidentification numbers and individual bit sequences of video and audiodata configuring the corresponding program are transmitted, and the PIDinformation, in which PCR is transmitted. The NIT transmits informationof the actual transmission network.

The PSIP table may include a virtual channel table (VCT), a system timetable (STT), a rating region table (RRT), an extended text table (ETT),a direct channel change table (DCCT), an event information table (EIT),and a master guide table (MGT). The VCT transmits information on virtualchannels, such as channel information for selecting channels andinformation such as packet identification (PID) numbers for receivingthe audio and/or video data. More specifically, when the VCT is parsed,the PID of the audio/video data of the broadcast program may be known.Herein, the corresponding audio/video data are transmitted within thechannel along with the channel name and the channel number. The STTtransmits information on the current data and timing information. TheRRT transmits information on region and consultation organs for programratings. The ETT transmits additional description of a specific channeland broadcast program. The EIT transmits information on virtual channelevents (e.g., program title, program start time, etc.). The DCCT/DCCSCTtransmits information associated with automatic (or direct) channelchange. And, the MGT transmits the versions and PID information of theabove-mentioned tables included in the PSIP.

Each of the above-described tables included in the PSI/PSIP isconfigured of a basic unit referred to as a “section” and a combinationof one or more sections forms a table. For example, the VCT may bedivided into 256 sections. Herein, one section may include a pluralityof virtual channel information. However, a single set of virtual channelinformation is not divided into two or more sections. At this point, thereceiving system may parse and decode the data for the data service thatare transmitting by using only the tables included in the PSI, or onlythe tables included in the PSIP, or a combination of tables included inboth the PSI and the PSIP. In order to parse and decode the data for thedata service, at least one of the PAT and PMT included in the PSI, andthe VCT included in the PSIP is required. For example, the PAT mayinclude the system information for transmitting the data correspondingto the data service, and the PID of the PMT corresponding to the dataservice data (or program number) The PMT may include the PID of the TSpacket used for transmitting the data service data. The VCT may includeinformation on the virtual channel for transmitting the data servicedata, and the PID of the TS packet for transmitting the data servicedata.

Meanwhile, depending upon the embodiment of the present invention, aDVB-SI may be applied instead of the PSIP. The DVB-SI may include anetwork information table (NIT), a service description table (SDT), anevent information table (EIT), and a time and data table (TDT). TheDVB-SI may be used in combination with the above-described PSI. Herein,the NIT divides the services corresponding to particular networkproviders by specific groups. The NTT includes all tuning informationthat is used during the IRD set-up. The NIT may be used for informing ornotifying any change in the tuning information. The SDT includes theservice name and different parameters associated with each servicecorresponding to a particular MPEG multiplex. The BIT is used fortransmitting information associated with all events occurring in theMPEG multiplex. The EIT includes information on the current transmissionand also includes information selectively containing differenttransmission streams that may be received by the IRD. And, the TDT isused for updating the clock included in the IRD.

Furthermore, three selective SI tables (i.e., a bouquet associate table(BAT), a running status table (RST), and a stuffing table (ST)) may alsobe included. More specifically, the bouquet associate table (BAT)provides a service grouping method enabling the IRD to provide servicesto the viewers. Each specific service may belong to at least one‘bouquet’ unit. A running status table (RST) section is used forpromptly and instantly updating at least one event execution status. Theexecution status section is transmitted only once at the changing pointof the event status. Other SI tables are generally transmitted severaltimes. The stuffing table (ST) may be used for replacing or discarding asubsidiary table or the entire SI tables.

In the present invention, the enhanced data included in the payloadwithin the TS packet consist of a digital storage media-command andcontrol (DSM-CC) section format. However, the TS packet including thedata service data may correspond either to a packetized elementarystream (PES) type or to a section type. More specifically, either thePES type data service data configure the TS packet, or the section typedata service data configure the TS packet. The TS packet configured ofthe section type data will be given as the example of the presentinvention. At this point, the data service data are includes in thedigital storage media-command and control (DSM-CC) section. Herein, theDSM-CC section is then configured of a 188-byte unit TS packet.

Furthermore, the packet identification of the TS packet configuring theDSM-CC section is included in a data service table (DST). Whentransmitting the DST, ‘0×95’?is assigned as the value of a stream_typefield included in the service location descriptor of the PMT or the VCT.More specifically, when the PMT or VCT stream_type field value is‘0×95’, the receiving system may acknowledge that data broadcastingincluding enhanced data (i.e., the enhanced data) is being received. Atthis point, the enhanced data may be transmitted by a data carouselmethod. The data carousel method corresponds to repeatedly transmittingidentical data on a regular basis.

At this point, according to the control of the data decoder 710, thedemultiplexer 703 performs section filtering, thereby discardingrepetitive sections and outputting only the non-repetitive sections tothe data decoder 710. The demultiplexer 703 may also output only thesections configuring desired tables (e.g., VCT) to the data decoder 710by section filtering. Herein, the VCT may include a specific descriptorfor the enhanced data. However, the present invention does not excludethe possibilities of the enhanced data being included in other tables,such as the PMT. The section filtering method may include a method ofverifying the PID of a table defined by the MGT, such as the VCT, priorto performing the section filtering process. Alternatively, the sectionfiltering method may also include a method of directly performing thesection filtering process without verifying the MGT, when the VCTincludes a fixed PID (i.e., a base PID). At this point, thedemultiplexer 703 performs the section filtering process by referring toa table_id field, a version_number field, a section_number field, etc.

As described above, the method of defining the PID of the VCT broadlyincludes two different methods. Herein, the PID of the VCT is a packetidentifier required for identifying the VCT from other tables. The firstmethod consists of setting the PID of the VCT so that it is dependent tothe MGT. In this case, the receiving system cannot directly verify theVCT among the many PSI and/or PSIP tables. Instead, the receiving systemmust check the PID defined in the MGT in order to read the VCT. Herein,the MGT defines the PID, size, version number, and so on, of diversetables. The second method consists of setting the PID of the VCT so thatthe PID is given a base PID value (or a fixed PID value), thereby beingindependent from the MGT. In this case, unlike in the first method, theVCT according to the present invention may be identified without havingto verify every single PID included in the MGT. Evidently, an agreementon the base PID must be previously made between the transmitting systemand the receiving system.

Meanwhile, in the embodiment of the present invention, the demultiplexer703 may output only an application information table (AIT) to the datadecoder 710 by section filtering. The AIT includes information on anapplication being operated in the receiving system for the data service.The AIT may also be referred to as an XAIT, and an AMT. Therefore, anytable including application information may correspond to the followingdescription. When the AIT is transmitted, a value of 0×05’?may beassigned to a stream_type field of the PMT. The AIT may includeapplication information, such as application name, application version,application priority, application ID, application status (i.e.,auto-start, user-specific settings, kill, etc.), application type (i.e.,Java or HTML), position (or location) of stream including applicationclass and data files, application platform directory, and location ofapplication icon.

In the method for detecting application information for the data serviceby using the AIT, component_tag, original_network_id,transport_stream_id, and service_id fields may be used for detecting theapplication information. The component_tag field designates anelementary stream carrying a DSI of a corresponding object carousel. Theoriginal_network_id field indicates a DVB-SI original_network_id of theTS providing transport connection. The transport_stream_id fieldindicates the MPEG TS of the TS providing transport connection, and theservice_id field indicates the DVB-SI of the service providing transportconnection. Information on a specific channel may be obtained by usingthe original_network_id field, the transport_stream_id field, and theservice_id field. The data service data, such as the application data,detected by using the above-described method may be stored in the secondmemory 711 by the data decoder 710.

The data decoder 710 parses the DSM-CC section configuring thedemultiplexed enhanced data. Then, the enhanced data corresponding tothe parsed result are stored as a database in the second memory 711. Thedata decoder 710 groups a plurality of sections having the same tableidentification (table_id) so as to configure a table, which is thenparsed. Thereafter, the parsed result is stored as a database in thesecond memory 711. At this point, by parsing data and/or sections, thedata decoder 710 reads all of the remaining actual section data that arenot section-filtered by the demultiplexer 703. Then, the data decoder710 stores the read data to the second memory 711. The second memory 711corresponds to a table and data carousel database storing systeminformation parsed from tables and enhanced data parsed from the DSM-CCsection. Herein, a table_id field, a section_number field, and alast_section_number field included in the table may be used to indicatewhether the corresponding table is configured of a single section or aplurality of sections. For example, TS packets having the PID of the VCTare grouped to form a section, and sections having table identifiersallocated to the VCT are grouped to form the VCT.

When the VCT is parsed, information on the virtual channel to whichenhanced data are transmitted may be obtained. The obtained applicationidentification information, service component identificationinformation, and service information corresponding to the data servicemay either be stored in the second memory 711 or be outputted to thedata broadcasting application manager 713. In addition, reference may bemade to the application identification information, service componentidentification information, and service information in order to decodethe data service data. Alternatively, such information may also preparethe operation of the application program for the data service.Furthermore, the data decoder 710 controls the demultiplexing of thesystem information table, which corresponds to the information tableassociated with the channel and events. Thereafter, an A.V PID list maybe transmitted to the channel manager 707.

The channel manager 707 may refer to the channel map 708 in order totransmit a request for receiving system-related information data to thedata decoder 710, thereby receiving the corresponding result. Inaddition, the channel manager 707 may also control the channel tuning ofthe tuner 701. Furthermore, the channel manager 707 may directly controlthe demultiplexer 703, so as to set up the A/V PID, thereby controllingthe audio decoder 704 and the video decoder 705. The audio decoder 704and the video decoder 705 may respectively decode and output the audiodata and video data demultiplexed from the main data packet.Alternatively, the audio decoder 704 and the video decoder 705 mayrespectively decode and output the audio data and video datademultiplexed from the enhanced data packet. Meanwhile, when theenhanced data include data service data, and also audio data and videodata, it is apparent that the audio data and video data demultiplexed bythe demultiplexer 703 are respectively decoded by the audio decoder 704and the video decoder 705. For example, an audio-coding (AC)-3 decodingalgorithm may be applied to the audio decoder 704, and a MPEG-2 decodingalgorithm may be applied to the video decoder 705.

Meanwhile, the native TV application manager 706 operates a nativeapplication program stored in the first memory 709, thereby performinggeneral functions such as channel change. The native application programrefers to software stored in the receiving system upon shipping of theproduct. More specifically, when a user request (or command) istransmitted to the receiving system through a user interface (UI), thenative TV application manger 706 displays the user request on a screenthrough a graphic user interface (GUI), thereby responding to the user'srequest. The user interface receives the user request through an inputdevice, such as a remote controller, a key pad, a jog controller, an atouch-screen provided on the screen, and then outputs the received userrequest to the native TV application manager 706 and the databroadcasting application manager 713. Furthermore, the native TVapplication manager 706 controls the channel manager 707, therebycontrolling channel-associated, such as the management of the channelmap 708, and controlling the data decoder 710. The native TV applicationmanager 706 also controls the GUI of the overall receiving system,thereby storing the user request and status of the receiving system inthe first memory 709 and restoring the stored information.

The channel manager 707 controls the tuner 701 and the data decoder 710,so as to managing the channel map 708 so that it can respond to thechannel request made by the user. More specifically, channel manager 707sends a request to the data decoder 710 so that the tables associatedwith the channels that are to be tuned are parsed. The results of theparsed tables are reported to the channel manager 707 by the datadecoder 710. Thereafter, based on the parsed results, the channelmanager 707 updates the channel map 70B and sets up a PID in thedemultiplexer 703 for demultiplexing the tables associated with the dataservice data from the enhanced data.

The system manager 712 controls the booting of the receiving system byturning the power on or off. Then, the system manager 712 stores ROMimages (including downloaded software images) in the first memory 709.More specifically, the first memory 709 stores management programs suchas operating system (OS) programs required for managing the receivingsystem and also application program executing data service functions.The application program is a program processing the data service datastored in the second memory 711 so as to provide the user with the dataservice. If the data service data are stored in the second memory 711,the corresponding data service data are processed by the above-describedapplication program or by other application programs, thereby beingprovided to the user. The management program and application programstored in the first memory 709 may be updated or corrected to a newlydownloaded program. Furthermore, the storage of the stored managementprogram and application program is maintained without being deleted evenif the power of the system is shut down. Therefore, when the power issupplied the programs may be executed without having to be newlydownloaded once again.

The application program for providing data service according to thepresent invention may either be initially stored in the first memory 709upon the shipping of the receiving system, or be stored in the first 709after being downloaded. The application program for the data service(i.e., the data service providing application program) stored in thefirst memory 709 may also be deleted, updated, and corrected.Furthermore, the data service providing application program may bedownloaded and executed along with the data service data each time thedata service data are being received.

When a data service request is transmitted through the user interface,the data broadcasting application manager 713 operates the correspondingapplication program stored in the first memory 709 so as to process therequested data, thereby providing the user with the requested dataservice. And, in order to provide such data service, the databroadcasting application manager 713 supports the graphic user interface(GUI). Herein, the data service may be provided in the form of text (orshort message service (SMS)), voice message, still image, and movingimage. The data broadcasting application manager 713 may be providedwith a platform for executing the application program stored in thefirst memory 709. The platform may be, for example, a Java virtualmachine for executing the Java program. Hereinafter, an example of thedata broadcasting application manager 713 executing the data serviceproviding application program stored in the first memory 709, so as toprocess the data service data stored in the second memory 711, therebyproviding the user with the corresponding data service will now bedescribed in detail.

Assuming that the data service corresponds to a traffic informationservice, the data service according to the present invention is providedto the user of a receiving system that is not equipped with anelectronic map and/or a GPS system in the form of at least one of a text(or short message service (SMS)), a voice message, a graphic message, astill image, and a moving image. In this case, is a GPS module ismounted on the receiving system shown in FIG. 13, the GPS modulereceives satellite signals transmitted from a plurality of low earthorbit satellites and extracts the current position (or location)information (e.g., longitude, latitude, altitude), thereby outputtingthe extracted information to the data broadcasting application manager713.

At this point, it is assumed that the electronic map includinginformation on each link and nod and other diverse graphic informationare stored in one of the second memory 711, the first memory 709, andanother memory that is not shown. More specifically, according to therequest made by the data broadcasting application manager 713, the dataservice data stored in the second memory 711 are read and inputted tothe data broadcasting application manager 713. The data broadcastingapplication manager 713 translates (or deciphers) the data service dataread from the second memory 711, thereby extracting the necessaryinformation according to the contents of the message and/or a controlsignal.

FIG. 14 illustrates a block diagram showing the structure of a digitalbroadcast (or television) receiving system according to anotherembodiment of the present invention. Referring to FIG. 14, the digitalbroadcast receiving system includes a tuner 801, a demodulating unit802, a demultiplexer 803, a first descrambler 804, an audio decoder 805,a video decoder BOG, a second descrambler 807, an authentication unitBOB, a native TV application manager 809, a channel manager 810, achannel map 811, a first memory 812, a data decoder 813, a second memory814, a system manager 815, a data broadcasting application manager 816,a storage controller 817, a third memory 818, and a telecommunicationmodule 819. Herein, the third memory 81B is a mass storage device, suchas a hard disk drive (HDD) or a memory chip. Also, during thedescription of the digital broadcast (or television or DTV) receivingsystem shown in FIG. 14, the components that are identical to those ofthe digital broadcast receiving system of FIG. 13 will be omitted forsimplicity.

As described above, in order to provide services for preventing illegalduplication (or copies) or illegal viewing of the enhanced data and/ormain data that are transmitted by using a broadcast network, and toprovide paid broadcast services, the transmitting system may generallyscramble and transmit the broadcast contents. Therefore, the receivingsystem needs to descrample the scrambled broadcast contents in order toprovide the user with the proper broadcast contents. Furthermore, thereceiving system may generally be processed with an authenticationprocess with an authentication means before the descrambling process.Hereinafter, the receiving system including an authentication means anda descrambling means according to an embodiment of the present inventionwill now be described in detail.

According to the present invention, the receiving system may be providedwith a descrambling means receiving scrambled broadcasting contents andan authentication means authenticating (or verifying) whether thereceiving system is entitled to receive the descrambled contents.Hereinafter, the descrambling means will be referred to as first andsecond descramblers 804 and 807, and the authentication means will bereferred to as an authentication unit 808. Such naming of thecorresponding components is merely exemplary and is not limited to theterms suggested in the description of the present invention. Forexample, the units may also be referred to as a decryptor. Although FIG.14 illustrates an example of the descramblers 804 and 807 and theauthentication unit 808 being provided inside the receiving system, eachof the descramblers 804 and 807 and the authentication unit 808 may alsobe separately provided in an internal or external module. Herein, themodule may include a slot type, such as a SD or CF memory, a memorystick type, a USB type, and so on, and may be detachably fixed to thereceiving system.

As described above, when the authentication process is performedsuccessfully by the authentication unit 808, the scrambled broadcastingcontents are descrambled by the descramblers 804 and 807, thereby beingprovided to the user. At this point, a variety of the authenticationmethod and descrambling method may be used herein. However, an agreementon each corresponding method should be made between the receiving systemand the transmitting system. Hereinafter, the authentication anddescrambling methods will now be described, and the description ofidentical components or process steps will be omitted for simplicity.

The receiving system including the authentication unit 808 and thedescramblers 804 and 807 will now be described in detail. The receivingsystem receives the scrambled broadcasting contents through the tuner801 and the demodulating unit 802. Then, the system manager 815 decideswhether the received broadcasting contents have been scrambled. Herein,the demodulating unit 802 may be included as a demodulating meansaccording to embodiments of the present invention as described in FIG. 8and FIG. 12. However, the present invention is not limited to theexamples given in the description set forth herein. If the systemmanager 815 decides that the received broadcasting contents have beenscrambled, then the system manager 815 controls the system to operatethe authentication unit 808. As described above, the authentication unit808 performs an authentication process in order to decide whether thereceiving system according to the present invention corresponds to alegitimate host entitled to receive the paid broadcasting service.Herein, the authentication process may vary in accordance with theauthentication methods.

For example, the authentication unit 808 may perform the authenticationprocess by comparing an IP address of an IP datagram within the receivedbroadcasting contents with a specific address of a corresponding host.At this point, the specific address of the corresponding receivingsystem (or host) may be a MAC address. More specifically, theauthentication unit 808 may extract the IP address from the decapsulatedIP datagram, thereby obtaining the receiving system information that ismapped with the IP address. At this point, the receiving system shouldbe provided, in advance, with information (e.g., a table format) thatcan map the IP address and the receiving system information.Accordingly, the authentication unit 808 performs the authenticationprocess by determining the conformity between the address of thecorresponding receiving system and the system information of thereceiving system that is mapped with the IP address. In other words, ifthe authentication unit 808 determines that the two types of informationconform to one another, then the authentication unit 808 determines thatthe receiving system is entitled to receive the correspondingbroadcasting contents.

In another example, standardized identification information is definedin advance by the receiving system and the transmitting system. Then,the identification information of the receiving system requesting thepaid broadcasting service is transmitted by the transmitting system.Thereafter, the receiving system determines whether the receivedidentification information conforms with its own unique identificationnumber, so as to perform the authentication process. More specifically,the transmitting system creates a database for storing theidentification information (or number) of the receiving systemrequesting the paid broadcasting service. Then, if the correspondingbroadcasting contents are scrambled, the transmitting system includesthe identification information in the EMM, which is then transmitted tothe receiving system.

If the corresponding broadcasting contents are scrambled, messages(e.g., entitlement control message (ECM), entitlement management message(EMM)), such as the CAS information, mode information, message positioninformation, that are applied to the scrambling of the broadcastingcontents are transmitted through a corresponding data header or antherdata packet. The ECM may include a control word (CW) used for scramblingthe broadcasting contents. At this point, the control word may beencoded with an authentication key. The EMM may include anauthentication key and entitlement information of the correspondingdata. Herein, the authentication key may be encoded with a receivingsystem-specific distribution key. In other words, assuming that theenhanced data are scrambled by using the control word, and that theauthentication information and the descrambling information aretransmitted from the transmitting system, the transmitting systemencodes the CW with the authentication key and, then, includes theencoded CW in the entitlement control message (ECM), which is thentransmitted to the receiving system. Furthermore, the transmittingsystem includes the authentication key used for encoding the CW and theentitlement to receive data (or services) of the receiving system (i.e.,a standardized serial number of the receiving system that is entitled toreceive the corresponding broadcasting service or data) in theentitlement management message (EMM), which is then transmitted to thereceiving system.

Accordingly, the authentication unit BOB of the receiving systemextracts the identification information of the receiving system and theidentification information included in the EMM of the broadcastingservice that is being received. Then, the authentication unit 808determines whether the identification information conform to each other,so as to perform the authentication process. More specifically, if theauthentication unit 808 determines that the information conform to eachother, then the authentication unit 808 eventually determines that thereceiving system is entitled to receive the request broadcastingservice.

In yet another example, the authentication unit 808 of the receivingsystem may be detachably fixed to an external module. In this case, thereceiving system is interfaced with the external module through a commoninterface (CI). In other words, the external module may receive the datascrambled by the receiving system through the common interface, therebyperforming the descrambling process of the received data. Alternatively,the external module may also transmit only the information required forthe descrambling process to the receiving system. The common interfaceis configured on a physical layer and at least one protocol layer.Herein, in consideration of any possible expansion of the protocol layerin a later process, the corresponding protocol layer may be configuredto have at least one layer that can each provide an independentfunction.

The external module may either consist of a memory or card havinginformation on the key used for the scrambling process and otherauthentication information but not including any descrambling function,or consist of a card having the above-mentioned key information andauthentication information and including the descrambling function. Boththe receiving system and the external module should be authenticated inorder to provide the user with the paid broadcasting service provided(or transmitted) from the transmitting system. Therefore, thetransmitting system can only provide the corresponding paid broadcastingservice to the authenticated pair of receiving system and externalmodule.

Additionally, an authentication process should also be performed betweenthe receiving system and the external module through the commoninterface. More specifically, the module may communicate with the systemmanager 815 included in the receiving system through the commoninterface, thereby authenticating the receiving system. Alternatively,the receiving system may authenticate the module through the commoninterface. Furthermore, during the authentication process, the modulemay extract the unique ID of the receiving system and its own unique IDand transmit the extracted IDs to the transmitting system. Thus, thetransmitting system may use the transmitted ID values as informationdetermining whether to start the requested service or as paymentinformation. Whenever necessary, the system manager 815 transmits thepayment information to the remote transmitting system through thetelecommunication module 819.

The authentication unit 808 authenticates the corresponding receivingsystem and/or the external module. Then, if the authentication processis successfully completed, the authentication unit 808 certifies thecorresponding receiving system and/or the external module as alegitimate system and/or module entitled to receive the requested paidbroadcasting service. In addition, the authentication unit 808 may alsoreceive authentication-associated information from a mobiletelecommunications service provider to which the user of the receivingsystem is subscribed, instead of the transmitting system providing therequested broadcasting service. In this case, theauthentication-association information may either be scrambled by thetransmitting system providing the broadcasting service and, then,transmitted to the user through the mobile telecommunications serviceprovider, or be directly scrambled and transmitted by the mobiletelecommunications service provider. Once the authentication process issuccessfully completed by the authentication unit 808, the receivingsystem may descramble the scrambled broadcasting contents received fromthe transmitting system. At this point, the descrambling process isperformed by the first and second descramblers 804 and 807. Herein, thefirst and second descramblers 804 and 807 may be included in an internalmodule or an external module of the receiving system.

The receiving system is also provided with a common interface forcommunicating with the external module including the first and seconddescramblers 804 and 807, so as to perform the descrambling process.More specifically, the first and second descramblers 804 and 807 may beincluded in the module or in the receiving system in the form ofhardware, middleware or software. Herein, the descramblers 804 and 807may be included in any one of or both of the module and the receivingsystem. If the first and second descramblers 804 and 807 are providedinside the receiving system, it is advantageous to have the transmittingsystem (i.e., at least any one of a service provider and a broadcaststation) scramble the corresponding data using the same scramblingmethod.

Alternatively, if the first and second descramblers 804 and 807 areprovided in the external module, it is advantageous to have eachtransmitting system scramble the corresponding data using differentscrambling methods. In this case, the receiving system is not requiredto be provided with the descrambling algorithm corresponding to eachtransmitting system. Therefore, the structure and size of receivingsystem may be simplified and more compact. Accordingly, in this case,the external module itself may be able to provide CA functions, whichare uniquely and only provided by each transmitting systems, andfunctions related to each service that is to be provided to the user.The common interface enables the various external modules and the systemmanager 815, which is included in the receiving system, to communicatewith one another by a single communication method. Furthermore, sincethe receiving system may be operated by being connected with at leastone or more modules providing different services, the receiving systemmay be connected to a plurality of modules and controllers.

In order to maintain successful communication between the receivingsystem and the external module, the common interface protocol includes afunction of periodically checking the status of the oppositecorrespondent. By using this function, the receiving system and theexternal module is capable of managing the status of each oppositecorrespondent. This function also reports the user or the transmittingsystem of any malfunction that may occur in any one of the receivingsystem and the external module and attempts the recovery of themalfunction.

In yet another example, the authentication process may be performedthrough software. More specifically, when a memory card having CASsoftware downloaded, for example, and stored therein in advanced isinserted in the receiving system, the receiving system receives andloads the CAS software from the memory card so as to perform theauthentication process. In this example, the CAS software is read outfrom the memory card and stored in the first memory 812 of the receivingsystem. Thereafter, the CAS software is operated in the receiving systemas an application program. According to an embodiment of the presentinvention, the CAS software is mounted on (or stored) in a middlewareplatform and, then executed. A Java middleware will be given as anexample of the middleware included in the present invention. Herein, theCAS software should at least include information required for theauthentication process and also information required for thedescrambling process.

Therefore, the authentication unit 808 performs authentication processesbetween the transmitting system and the receiving system and alsobetween the receiving system and the memory card. At this point, asdescribed above, the memory card should be entitled to receive thecorresponding data and should include information on a normal receivingsystem that can be authenticated. For example, information on thereceiving system may include a unique number, such as a standardizedserial number of the corresponding receiving system. Accordingly, theauthentication unit 808 compares the standardized serial number includedin the memory card with the unique information of the receiving system,thereby performing the authentication process between the receivingsystem and the memory card.

If the CAS software is first executed in the Java middleware base, thenthe authentication between the receiving system and the memory card isperformed. For example, when the unique number of the receiving systemstored in the memory card conforms to the unique number of the receivingsystem read from the system manager 815, then the memory card isverified and determined to be a normal memory card that may be used inthe receiving system. At this point, the CAS software may either beinstalled in the first memory 812 upon the shipping of the presentinvention, or be downloaded to the first memory 812 from thetransmitting system or the module or memory card, as described above.Herein, the descrambling function may be operated by the databroadcasting application manger 816 as an application program.

Thereafter, the CAS software parses the EMM/ECM packets outputted fromthe demultiplexer 803, so as to verify whether the receiving system isentitled to receive the corresponding data, thereby obtaining theinformation required for descrambling (i.e., the CW) and providing theobtained CW to the descramblers 804 and 807. More specifically, the CASsoftware operating in the Java middleware platform first reads out theunique (or serial) number of the receiving system from the correspondingreceiving system and compares it with the unique number of the receivingsystem transmitted through the EMM, thereby verifying whether thereceiving system is entitled to receive the corresponding data. Once thereceiving entitlement of the receiving system is verified, thecorresponding broadcasting service information transmitted to the ECMand the entitlement of receiving the corresponding broadcasting serviceare used to verify whether the receiving system is entitled to receivethe corresponding broadcasting service. Once the receiving system isverified to be entitled to receive the corresponding broadcastingservice, the authentication key transmitted to the EMM is used to decode(or decipher) the encoded CW, which is transmitted to the ECM, therebytransmitting the decoded CW to the descramblers 804 and 807. Each of thedescramblers 804 and 807 uses the CW to descramble the broadcastingservice.

Meanwhile, the CAS software stored in the memory card may be expanded inaccordance with the paid service which the broadcast station is toprovide. Additionally, the CAS software may also include otheradditional information other than the information associated with theauthentication and descrambling. Furthermore, the receiving system maydownload the CAS software from the transmitting system so as to upgrade(or update) the CAS software originally stored in the memory card. Asdescribed above, regardless of the type of broadcast receiving system,as long as an external memory interface is provided, the presentinvention may embody a CAS system that can meet the requirements of alltypes of memory card that may be detachably fixed to the receivingsystem. Thus, the present invention may realize maximum performance ofthe receiving system with minimum fabrication cost, wherein thereceiving system may receive paid broadcasting contents such asbroadcast programs, thereby acknowledging and regarding the variety ofthe receiving system. Moreover, since only the minimum applicationprogram interface is required to be embodied in the embodiment of thepresent invention, the fabrication cost may be minimized, therebyeliminating the manufacturer's dependence on CAS manufacturers.Accordingly, fabrication costs of CAS equipments and management systemsmay also be minimized.

Meanwhile, the descramblers 804 and 807 may be included in the moduleeither in the form of hardware or in the form of software. In this case,the scrambled data that being received are descrambled by the module andthen demodulated. Also, if the scrambled data that are being receivedare stored in the third memory 818, the received data may be descrambledand then stored, or stored in the memory at the point of being receivedand then descrambled later on prior to being played (or reproduced).Thereafter, in case scramble/descramble algorithms are provided in thestorage controller 817, the storage controller 817 scrambles the datathat are being received once again and then stores the re-scrambled datato the third memory 818.

In yet another example, the descrambled broadcasting contents(transmission of which being restricted) are transmitted through thebroadcasting network. Also, information associated with theauthentication and descrambling of data in order to disable thereceiving restrictions of the corresponding data are transmitted and/orreceived through the telecommunications module 819. Thus, the receivingsystem is able to perform reciprocal (or two-way) communication. Thereceiving system may either transmit data to the telecommunicationmodule within the transmitting system or be provided with the data fromthe telecommunication module within the transmitting system. Herein, thedata correspond to broadcasting data that are desired to be transmittedto or from the transmitting system, and also unique information (i.e.,identification information) such as a serial number of the receivingsystem or MAC address.

The telecommunication module 819 included in the receiving systemprovides a protocol required for performing reciprocal (or two-way)communication between the receiving system, which does not support thereciprocal communication function, and the telecommunication moduleincluded in the transmitting system. Furthermore, the receiving systemconfigures a protocol data unit (PDU) using a tag-length-value (TLV)coding method including the data that are to be transmitted and theunique information (or ID information). Herein, the tag field includesindexing of the corresponding PDU. The length field includes the lengthof the value field. And, the value field includes the actual data thatare to be transmitted and the unique number (e.g., identificationnumber) of the receiving system.

The receiving system may configure a platform that is equipped with theJava platform and that is operated after downloading the Javaapplication of the transmitting system to the receiving system throughthe network. In this case, a structure of downloading the PDU includingthe tag field arbitrarily defined by the transmitting system from astorage means included in the receiving system and then transmitting thedownloaded PDU to the telecommunication module 819 may also beconfigured. Also, the PDU may be configured in the Java application ofthe receiving system and then outputted to the telecommunication module819. The PDU may also be configured by transmitting the tag value, theactual data that are to be transmitted, the unique information of thecorresponding receiving system from the Java application and byperforming the TLV coding process in the receiving system. Thisstructure is advantageous in that the firmware of the receiving systemis not required to be changed even if the data (or application) desiredby the transmitting system is added.

The telecommunication module within the transmitting system eithertransmits the PDU received from the receiving system through a wirelessdata network or configures the data received through the network into aPDU which is transmitted to the host. At this point, when configuringthe PDU that is to be transmitted to the host, the telecommunicationmodule within the transmitting end may include unique information (e.g.,IP address) of the transmitting system which is located in a remotelocation. Additionally, in receiving and transmitting data through thewireless data network, the receiving system may be provided with acommon interface, and also provided with a WAP, CDMA 1x EV-DO, which canbe connected through a mobile telecommunication base station, such asCDMA and GSM, and also provided with a wireless LAN, mobile internet,WiBro, WiMax, which can be connected through an access point. Theabove-described receiving system corresponds to the system that is notequipped with a telecommunication function. However, a receiving systemequipped with telecommunication function does not require thetelecommunication module 819.

The broadcasting data being transmitted and received through theabove-described wireless data network may include data required forperforming the function of limiting data reception. Meanwhile, thedemultiplexer 803 receives either the real-time data outputted from thedemodulating unit 802 or the data read from the third memory 818,thereby performing demultiplexing. In this embodiment of the presentinvention, the demultiplexer 803 performs demultiplexing on the enhanceddata packet. Similar process steps have already been described earlierin the description of the present invention. Therefore, a detailed ofthe process of demultiplexing the enhanced data will be omitted forsimplicity.

The first descrambler 804 receives the demultiplexed signals from thedemultiplexer 803 and then descrambles the received signals. At thispoint, the first descrambler 804 may receive the authentication resultreceived from the authentication unit 808 and other data required forthe descrambling process, so as to perform the descrambling process. Theaudio decoder 805 and the video decoder 806 receive the signalsdescrambled by the first descrambler 804, which are then decoded andoutputted. Alternatively, if the first descrambler 804 did not performthe descrambling process, then the audio decoder 805 and the videodecoder 806 directly decode and output the received signals. In thiscase, the decoded signals are received and then descrambled by thesecond descrambler 807 and processed accordingly.

As described above, the present invention has the following advantages.More specifically, the present invention is highly protected against (orresistant to) any error that may occur when transmitting additional datathrough a channel. And, the present invention is also highly compatibleto the conventional receiving system. Moreover, the present inventionmay also receive the additional data without any error even in channelshaving severe ghost effect and noise.

Additionally, by grouping a plurality of enhanced data packets, bylayering the group to a plurality of areas when multiplexing the groupwith the main data and transmitting the multiplexed data, and byidentifying the data type, processing method, and so on according to thecharacteristic of each layered area, the receiving function of thereceiving system may be enhanced. Furthermore, by performing at leastany one of the error correction coding process and the error detectioncoding process on the enhanced data, and by performing a row permutationprocess, the enhanced data may become robust, thereby being able to takestrong countermeasures against the constantly changing channelenvironment. Finally, the present invention is even more effective inproviding robustness when applied to mobile and portable receivers,which are also liable to a frequent change in channel and which requirerobustness against intense noise.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A digital television (DTV) transmitting system for processing digitalbroadcast data, the DTV transmitting system comprising: a Reed-Solomon(RS) frame encoder for generating an RS frame by adding RS parity datato bottom ends of columns of an RS frame payload and adding CyclicRedundancy Check (CRC) checksum data to right ends of rows of the RSframe payload, the RS frame payload including enhanced data; a blockprocessor for encoding the RS-CRC encoded enhanced data with a codingrate of 1/H, where H is an integer greater than 1; a group formatter formapping a portion of the enhanced data encoded with the coding rate of1/H into a data group and adding known data sequences and signalinginformation into the data group, and inserting place holders for maindata, MPEG headers, and RS parity data into the data group; a trellisencoder for trellis encoding the data group; and a transmitting unit formodulating the trellis-encoded data group and transmitting the modulateddata group.
 2. The DTV transmitting system of claim 1, wherein the groupformatter further inserts trellis initialization data into the datagroup required for initializing the trellis encoder.
 3. The DTVtransmitting system of claim 1, wherein the group formatterdeinterleaves the data group including the place holders.
 4. The DTVtransmitting system of claim 3, further comprising: a multiplexer formultiplexing the data in the deinterleaved data group with main data;and an interleaver for interleaving the multiplexed data.
 5. The DTVtransmitting system of claim 1, wherein at least two of the known datasequences have different lengths and the signaling information comprisesinformation associated with the data group.
 6. A method of processingdigital broadcast data in a digital television (DTV) transmittingsystem, the method comprising: generating, by a Reed-Solomon (RS) frameencoder, an RS frame by adding RS parity data to bottom ends of columnsof an RS frame payload and adding Cyclic Redundancy Check (CRC) checksumdata to right ends of rows of the RS frame payload, the RS frame payloadincluding enhanced data; encoding, by a block processor, the RS-CRCencoded enhanced data with a coding rate of 1/H, where H is an integergreater than 1; mapping, by a group formatter, a portion of the enhanceddata encoded with the coding rate of 1/H into a data group and addingknown data sequences and signaling information into the data group;inserting, by the group formatter, place holders for main data, MPEGheaders, and RS parity data into the data group; trellis encoding thedata group in a trellis encoder; and modulating the trellis-encoded datagroup and transmitting the modulated data group.
 7. The method of claim6, wherein the group formatter inserts trellis initialization data intothe data group required for initializing the trellis encoder.
 8. Themethod of claim 6, wherein the group formatter deinterleaves the datagroup including the place holders.
 9. The method of claim 8, furthercomprising: multiplexing the data in the deinterleaved data group withmain data; and interleaving the multiplexed data.
 10. The method ofclaim 6, wherein at least two of the known data sequences have differentlengths and the signaling information includes information associatedwith the data group.
 11. A digital television (DTV) receiving system forprocessing digital broadcast data, the DTV receiving system comprising:a tuner for receiving a broadcast signal comprising at least one datagroup, each data group having first and second data regions, the firstdata region comprising main data and enhanced data, the second dataregion comprising enhanced data, known data sequences, and signalinginformation; a demodulator for demodulating the broadcast signal; anequalizer for compensating a channel distortion of the broadcast signalusing at least one of the known data sequences; an inner decoder forinner decoding the equalized signal; an outer decoder for outer decodingthe inner-decoded signal; and an RS frame decoder for building an RSframe and correcting errors in the RS frame, wherein the RS framecomprises an RS frame payload, RS parity data added to bottom ends ofcolumns of the RS frame payload, and CRC checksum data added to rightends of rows of the RS frame payload, the RS frame payload including theenhanced data in the at least one data group.
 12. The DTV receivingsystem of claim 11, wherein the equalizer equalizes the enhanced data inthe second data region by interpolating at least two channel impulseresponses (CIRs) estimated using at least one of the known datasequences.
 13. The DTV receiving system of claim 11, wherein theequalizer equalizes the enhanced data in the first data region byextrapolating at least two channel impulse responses (CIRs) estimatedusing at least one of the known data sequences.
 14. A method ofprocessing digital broadcast data in a digital television (DTV)receiving system, the method comprising: receiving a broadcast signalcomprising at least one data group, each data group having first andsecond data regions, the first data region comprising main data andenhanced data, the second data region comprising enhanced data, knowndata sequences, and signaling information; demodulating the broadcastsignal; compensating a channel distortion of the broadcast signal usingat least one of the known data sequences; inner decoding the equalizedsignal; outer decoding the inner-decoded signal; and building an RSframe and correcting errors in the RS frame, wherein the RS framecomprises an RS frame payload, RS parity data added to bottom ends ofcolumns of the RS frame payload, and CRC checksum data added to rightends of rows of the RS frame payload, the RS frame payload including theenhanced data in the at least one data group.
 15. The method of claim14, wherein the enhanced data in the second data region are equalized byinterpolating at least two channel impulse responses (CIRs) estimatedusing at least one of the known data sequences.
 16. The method of claim14, wherein the enhanced data in the first data region are equalized byextrapolating at least two channel impulse responses (CIRs) estimatedusing at least one of the known data sequences.